LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


GIFT    OF 


Cto 


IV. 


LUNAR    AND    HAWAIIAN    PHYSICAL    FEATURES    COMPARED. 


BY 


WILLIAM    H.    PICKERING. 


WITH    SIXTEEN   PLATES. 


PRESENTED  FEBRUARY  9,  1906.      RECEIVED  APRIL  7,  1906. 


MOKUAWEOWEO   AT   NlGHT. 

Compare  with  Figure  18  taken  at  about  the  same  date. 


LUNAR   AND   HAWAIIAN  PHYSICAL  FEATURES  COMPARED. 

THE  lunar  surface  presents  such  a  strong  contrast  to  the  more  thickly  populated 
portions  of  the  Earth,  that  little  resemblance  between  them  can  be  traced.  It  has 
therefore  naturally  proved  very  difficult  to  explain  the  nature  and  origin  of  many  of 
the  features  of  our  satellite.  Even  those  of  our  volcanic  regions  which  have  been 
most  extensively  studied,  show  little  analogy  to  the  Moon.  There  are  other  regions, 
however,  notably  in  the  Hawaiian  Islands,  where  an  entirely  different  class  of  volcanic 
phenomena  are  exhibited.  These  it  is  now  found  bear  a  striking  resemblance  in  some, 
respects  to  what  we  find  upon  our  satellite.  Although  the  Hawaiian  craters  are  mostly 
extinct,  or  at  present  inactive,  yet  they  are  the  only  ones  known  of  this  type  exhibit- 
ing any  activity  whatever. 

In  view  of  these  facts  the  writer  determined  to  visit  the  Hawaiian  Islands  in  the 
summer  of  1905,  and  study  their  volcanic  features  with  especial  reference  to  those 
found  upon  the  Moon.  In  Hawaii  a  considerable  number  of  the  craters  are  of  the 
engulfment  type,  as  distinguished  from  those  of  the  explosive  type,  so  well  developed 
in  southern  Europe.  In  the  latter  class  a  high  truncated  cone  is  built  up  by  mild 
eruptions  of  steam  and  cinders,  sometimes  alternating  with  lava.  At  long  intervals 
violent  explosions  occur,  which  sometimes  blow  away  a  large  portion  of  the  summit, 
thus  entirely  changing  the  shape  of  the  mountain.  Such  an  explosion  of  steam 
occurred  in  Vesuvius  at  the  time  of  the  destruction  of  Pompeii,  and  a  still  more  violent 
one  in  Krakatoa  in  1883.  Nothing  whatever  of  this  sort  is  found  upon  the  Moon.  In 
volcanoes  of  the  engulfment  type  on  the  other  hand,  comparatively  little  steam  is 
evolved,  often  there  is  no  exterior  cone,  and  the  craters  enlarge  quietly  by  the  crack- 
ing off  and  falling  in  of  their  walls. 

The  Hawaiian  structures,  although  similar  to  those  of  the  Moon,  are  comparatively  ' 
on  a  very  small  scale,  and  their  dimensions  must  often  be  multiplied  by  a  factor  of 
from  100  in  the  case  of  the  older  craters,  to  300  in  the  case  of  the  more  recent  ones, 
in  order  to  equal  the  dimensions  of  the  similar  formations  found  upon  our  satellite. 
This  applies  especially  to  horizontal  distances,  —  vertically  a  factor  of  from 
20  more  nearly  represents  the  proper  proportion. 


152  PICKERING.  —  LUNAR   AND    HAWAIIAN    PHYSICAL    FEATURES    COMPARED. 

The  force  of  gravitation  at  the  surface  of  the  Moon  is  but  one- sixth  as  great  as  it  is 
upon  the  Earth,  and  this  difference  is  usually  given  as  the  cause  of  the  great  compara- 
tive size  of  the  lunar  formations.  On  the  old  theory  that  the  lunar  craters  were  due 
to  explosions  of  steam,  like  our  explosive  volcanoes,  it  was  evident  that  matter 
expelled  from  a  crater  vent  could  be  thrown  six  times  as  far  as  upon  the  Earth. 
Although  this  theory  is  now  practically  abandoned,  gravitation  would  still  have  an 
influence  on  the  relative  size,  since  a  cliff  or  pinnacle  upon  the  Moon  could  be  six 
times  the  height  of  one  upon  the  Earth,  and  yet  exert  no  greater  crushing  force  on 
the  material  beneath  it.  Still  it  is  very  evident  that  this  explanation  alone  is  inade- 
quate to  account  for  the  great  difference  in  size  actually  observed. 

The  facts  seem  to  be  that  we  are  really  trying  to  compare  objects  formed  under 
entirely  different  conditions.  The  larger  craters  on  the  Moon  came  into  existence 
when  the  thin,  solid  crust  covering  the  molten  interior  was,  owing  to  the  solidifica- 
tion and  contraction  of  the  crust,  much  too  small  to  contain  the  liquid  material. 
The  craters  were  therefore  formed  by  the  lava  bursting  through  the  crust,  and 
so  relieving  the  pressure. 

Later,  after  this  relief  had  been  found,  and  the  crust  had  thickened,  the  interior 
regions  by  cooling  shrank  away  from  the  solid  shell  which  was  now  too  large,  and 
being  insufficiently  supported  caved  in,  permitting  the  great  fissure  eruptions  which 
produced  the  tnaria.  These  extensive  outflows  of  lava  dissolved  the  original  solid 
shell  wherever  they  came  in  contact  with  it  much  as  they  do  at  the  present  day  in 
Hawaii.  Had  the  Moon  been  much  smaller,  these  extensive  eruptions  would  not 
have  attained  such  relatively  great  size,  or  might  even  not  have  occurred  at  all.  On 
the  other  hand,  had  the  Moon  been  larger,  their  relative  size  would  have  been  greater, 
since  the  volume  of  the  sphere  would  have  been  larger  in  proportion  to  its  surface  and 
would  therefore  have  shrunk  more  in  proportion.  This  was  precisely  what  took  place 
upon  the  Earth  in  all  probability :  our  original  gigantic  craters  were  destroyed  by  the 
outflow  of  the  earlier  archaic  rocks,  which  completely  submerged  and  dissolved  them. 
Our  present  Hawaiian  craters  must  therefore  be  compared,  not  with  the  primary 
formations  still  left  upon  our  Moon,  but  rather  with  the  secondary  ones  formed 
later  upon  the  surface  of  its  maria.  Of  these  Bessel,  twelve  miles  in  diameter, 
is  a  large  and  well  known  example.  From  this  size  down  countless  craterlets  are 
known. 

Three  craters  are  found  upon  the  Earth  measuring  about  fifteen  miles  in  diameter. 
They  occur  in  Kamchatka,  in  Japan,  and  in  the  Philippines,  but  are  all  of  the  explo- 
sive type,  and  therefore  not  comparable  to  those  found  on  the  Moon.  It  is  possible 


PICKERING. —  LUNAR   AND   HAWAIIAN    PHYSICAL   FEATURES    COMPARED.  153 

that  a  large  engulfment  crater  formerly  existed  upon  Kauai,  and  another  in  southern 
Hawaii,  near  the  coast,  south  of  Mauna  Loa,  but  the  writer  was  unable  to  examine 
either  of  these  regions  during  his  recent  visit.  The  latter  crater  must  have  been 
about  five  miles  in  diameter,  the  former  perhaps  much  larger.  The  largest  engulf- 
ment crater  known  is  Crater  Lake,  Oregon,  measuring  five  by  six  miles  in  diameter 
with  a  depth  of  about  3,000  feet.  Next  to  it  comes  Haleakala  in  the  Island  of 
Maui,  Hawaii,  measuring  seven  miles  in  length  by  two  in  width.  It  is  about  2,000 
feet  deep. 

The  secondary  craters  found  upon  the  lunar  maria  are  so  small  that  it  is  impos- 
sible to  study  their  interiors  to  advantage;  we  shall  therefore  content  ourselves 
with  comparing  the  Hawaiian  formations,  as  far  as  possible  with  the  large  pri- 
mary formations  of  the  Moon,  without  regard  to  the  great  discrepancy  in  their 
relative  size. 

On  the  Hawaiian  Islands  with  the  exception  of  the  three  groat  craters  of 
Haleakala,  Mokuaweoweo,  and  Kilauea,  few  of  the  crater  pits  exceed  half  a  mile  in 
diameter,  measured  on  their  crater  floors,  or  former  free  liquid  lava  surfaces,  although 
there  are  probably  several  hundred  pits  over  200  feet  in  diameter.  In  addition  to 
these  are  countless  cinder  cones,  ^piracies,  etc.  On  the  Earth  at  present  the  cooling 
process  always  intervenes  before  great  size  is  attained.  Doubtless  formerly  the  lava 
was  hotter  when  it  first  issued  from  the  interior  than  it  is  now,  also  the  solid  crust 
resting  on  the  liquid  mass  was  thinner,  so  that  the  channel  communicating  with  the 
interior  was  shorter  and  of  greater  diameter,  thus  offering  a  freer  passage  to  the 

liquid  flow. 

Terrestrial  craters  may  be  divided  into  three  classes,  according  to  the  materials  of 
which  they  are  composed.  These  are  (a)  tuff  or  tufa  cones,  which  are  made  of 
hardened  volcanic  mud,  (b)  cinder  cones,  made  of  scoria,  lapilli,  or  sand,  that  is,  lava 
broken  up  into  masses  of  varying  size,  by  the  action  of  steam,  from  stones  several 
inches  or  even  feet  in  diameter  to  fine  powder,  and  (c)  lava  craters,  where  the  lava 
occurs  in  unbroken  masses.  It  is  this  third  class,  where  less  water  is  involved  in  the 
eruption,  which  most  resembles  what  we  find  upon  the  Moon.  Representatives  of  all 
three  classes  are  to  be  found  in  Hawaii.  Many  volcanoes  like  Vesuvius  eject  both 

cinders  and  lava. 

The  third  class  may  again  be  divided  into  four  subdivisions  according  to  the 
of  the  craters,  namely:  lava  cones,  lava  pits,^a  rings,  and  lava  bowls. 
sometimes  of  small  size,  the  lava  cones  often  emit  vast  volumes  of  lava,  which  t 
the  form  of  broad  streams  may  extend  for  many  miles.    The  lava  pits  are  by  far  the 


154  PICKERING.  —  LUNAR  AND    HAWAIIAN   PHYSICAL   FEATURES    COMPARED. 

most  numerous  group,  and  most  widely  distributed  throughout  the  islands.  They 
have  no  outer  slopes  whatever,  consisting  simply  of  a  pit  sunk  in  the  ground.  Their 
walls  are  sometimes  vertical,  descending  without  talus  to  a  flat  floor ;  sometimes  the 
talus  is  present,  and  may  cover  the  whole  floor,  leaving  the  bottom  as  a  conical  pit. 
Sometimes  the  walls  are  inclined,  descending  at  a  uniform  slope  to  a  flat  floor.  The 
slope  in  this  case  is  usually  steep,  —  perhaps  45°.  The  crater  rings  are  the  rarest 
type,  and  resemble  the  larger  craters  found  upon  the  Moon.  They  have  flat  floors 
and  sloping  inner  and  outer  walls.  The  crater  bowls  differ  from  them  in  that  the 
bottom  instead  of  presenting  a  well-defined  flattened  floor  is  concave,  the  curvature 
being  continuous  with  that  of  the  walls.  They  are  identical  in  appearance  with 
most  of  the  smaller  lunar  craters.  Section  drawings  illustrating  these  different  forms 
will  be  found  on  p.  171,  and  will  be  described  when  the  various  types  are  reached. 
Photographs  of  many  of  them  are  also  given  at  the  end  of  this  memoir. 

In  addition  to  the  craters,  there  are  found  numerous  other  interesting  formations, 
such  as  lava  caves,  channels,  cracks,  spiracles,  pinnacles,  ridges,  etc.  A  spiracle  is 
literally  a  blow  hole,  but  in  this  paper,  for  lack  of  a  better  name,  I  have  used  the 
word  to  indicate  the  solid  formation  surrounding  the  hole.  In  dealing  with  these 
various  objects  it  has  been  thought  best  to  describe  each  class  by  itself,  stating  where 
the  best  specimens  of  each  may  be  seen. 

The  visitor  to  Hawaii,  on  entering  the  harbor  of  Honolulu,  is  at  once  struck  with 
two  very  conspicuous  volcanic  formations,  known  as  Diamond  Head  and  the  Punch- 
bowl. Other  smaller  and  less  conspicuous  craters,  of  the  same  general  type,  will  be 
found  in  the  immediate  vicinity.  The  Punchbowl,  «,  p.  171,  reaches  an  altitude  of 
498  feet,  and  is  situated  within  the  city  limits.  The  crater  is  but  slightly  concave, 
being  filled  nearly  to  the  brim,  and  has  a  diameter  of  2500  feet.  The  writer  did 
not  have  an  opportunity  to  examine  it  carefully,  but  as  it  was  evidently  similar 
to  Diamond  Head,  6,  p.  171,  which  was  larger,  and  apparently  better  preserved,  this 
was  not  greatly  regretted. 

From  every  direction  Diamond  Head,  Figure  1,  presents  an  appearance  similar  to 
a  lunar  crater.  Its  highest  point  reaches  an  altitude  of  only  761  feet  above  the  sea, 
while  the  diameter  of  the  crater  rim  measures  3200  by  3700  feet.  An  ascent  of 
the  rim  on  foot  is  easily  made  from  a  point  on  the  road  just  beyond  the  terminus  of 
the  electric  car  line.  The  rim  at  this  point  has  an  altitude  of  450  feet.  In  the 
interior  of  the  crater,  somewhat  to  one  side  of  the  centre,  is  located  a  shallow  lake, 
sometimes  dry,  whose  bed  measures  220  feet  below  the  rim  where  we  crossed  it.  It  is 
surrounded  by  a  very  dense  growth  of  thorny  shrubs.  Within  the  crater  was  found 


155 

ocean 


PICKERING.- LUNAR  AND   HAWAIIAN   PHYSICAL   FEATURES   COMPARED. 

a  specimen  containing  a  fossil  shell,  which  was  doubtless  brought  up  from  the  „ 
bed  by  the  erupted  material  when  the  crater  was  active.  A  branching  system  of 
cracks,  none  of  them  exceeding  three  inches  in  width,  was  found  in  one  place. 
The  inner  slopes  of  the  crater  range  from  20°  to  45°,  the  outer  from  30°  to  7<T 
Clearly  the  walls  were  formerly  somewhat  higher,  and  the  interior  and  exterior  of  the 
crater  about  on  a  level.  The  edge  of  the  rim  is  extremely  sharp  in  places.  The 
material  is  composed  of  a  hardened  volcanic  mud  or  tuff,  and  while  the  crater  some- 
what resembles  numerous  of  the  smaller  lunar  craterlets,  yet  their  interiors  are  always 
at  a  lower  level  than  the  exterior  plane  on  which  they  are  situated,  and  their  inner 
slopes  are  steeper  than  their  outer  ones.  The  crater  seems  to  offer  little  analogy 
therefore  to  the  formations  upon  the  Moon. 

Cinder  cones,  c  p.  171,  form  the  most  numerous  class  of  craters  in  Hawaii.  They 
are  found  scattered  over  the  summit  of  Mauna  Kea,  in  the  valley  between  Mauna  Kea 
and  Mauna  Loa,  in  the  interior  of  Haleakala,  along  the  southern  and  northwestern 
coasts  of  Hawaii,  and  in  many  other  places.  A  group  situated  near  the  summit  of 
Mauna  Kea  is  shown  in  Figure  2.  They  have  all  the  characteristics  of  explosive  vol- 
canoes like  Vesuvius,  although  their  craters  are  larger  in  proportion  to  the  height  of 
their  cones.  So  far  as  is  known 'they  bear  no  analogy  to  anything  found  upon  the 
Moon. 

The  third  class,  or  lava  craters,  on  the  other  hand,  present  a  close  resemblance  in 
many  respects  to  some  of  the  lunar  formations,  and  we  shall  therefore  describe  them 
in  detail.  The  first  subdivision,  the  lava  cones,  are  most  strikingly  represented  by 
Mauna  Loa,  by  far  the  world's  largest  volcano.  It  and  Mauna  Kea  are  also  our 
highest  mountains  if  we  measure  in  every  case  from  the  mountain's  base.  For  the 
Hawaiian  volcanoes  the  base  lies  15,000  feet  below  the  level  of  the  sea.  Nevertheless, 
the  summit  crater  of  Mauna  Loa  is  so  large  in  proportion  to  its  depth  that  it  was 
thought  best  to  select  a  small  lava  cone  in  Haleakala  as  the  typical  example  of  this 
form  of  crater.  This  cone  is  shown  in  the  right  foreground  of  Figure  3,  and  its  sec- 
tion at  e  on  p.  171.  The  outer  slopes  of  a  lava  cone  are  often  covered  by  loose  cinders, 
as  in  the  present  case,  and  the  inner  slopes  may  be  inclined  like  those  of  a  cinder  cone, 
although  they  are  generally  much  steeper,  but  if  the  inner  walls  are  of  lava  its  classi- 
fication is  assured.  Lava  sometimes  issues  from  the  summits  of  these  cones,  but  some- 
times it  comes  directly  out  of  the  ground,  as  in  Kilauea  Iki  and  at  Huehue,  —  no  trace 
of  a  cone  being  found. 

Lava  has  not  been  known  within  historic  times  to  overflow  the  summit  crater  of 
Mauna  Loa,  but  it  escapes  from  just  below  the  summit,  outside  the  crater  walls,  in 


156  PICKERING.  —  LUNAR   AND    HAWAIIAN    PHYSICAL    FEATURES    COMPARED. 

enormous  quantities,  especially  upon  the  northeastern  side.  The  vast  bulk  of  the 
mountain  seems  to  have  been  built  up  largely  from  these  emissions,  and  the  same  is 
true  also  of  Mt.  Etna  in  Sicily.  It  is  characteristic  of  these  mountains  that  their 
slopes  are  much  more  gentle  than  those  of  cinder  cones,  and  this  is  especially  true 
of  Mauna  Loa,  Figure  4.  The  summit  of  this  mountain  is  13,675  feet  in  elevation. 
The  view  was  taken  from  the  north,  and  represents  the  upper  7000  feet  of  the  moun- 
tain. The  summit  is  very  difficult  of  access  on  account  of  the  exceedingly  rough 
nature  of  the  ground,  the  total  absence  of  water,  and  on  account  of  its  flatness  of 
the  long  distance  of  the  summit  from  a  base  of  supplies.  It  is  probably  best  reached 
from  the  Kona,  or  western  side,  by  way  of  Kealakekua  Bay. 

The  slopes  of  Etna  are  heavily  buttressed  by  ridges,  formed  each  of  a  separate 
lava  stream,  which  has  flowed  from  the  small  lava  cones  upon  the  flanks  of  the 
mountain.  This  structure  is  also  well  shown  in  the  lunar  crater  Bullialdus,  Figure  5. 
The  diameter  of  this  crater  is  38  miles.  Since  these  streams  sometimes  cross  one 
another,  leaving  diamond-shaped  hollows  between  them,  it  is  obvious  that  the 
formation  cannot  be  due  to  the  grooving  of  a  smooth  surface  by  erosion,  but  must 
really  be  formed  by  projecting  ridges.  We  shall  refer  again  to  this  matter  in  con- 
nection with  Clavius  and  Kilauea  Iki.  We  thus  have  indirect  evidence  of  the  exist- 
ence of  lava  cones  upon  the  Moon,  as  the  source  of  these  streams. 

Until  recently  this  was  all  the  evidence  we  had.  The  tall  volcanic  cone  with  the 
comparatively  minute  crater  at  its  summit,  so  characteristic  of  the  typical  terrestrial 
volcano,  was  supposed  to  be  absent  from  the  Moon.  In  the  terrestrial  volcano  the 
floor  of  the  crater  is  always  higher  than  its  base ;  on  the  Moon  the  reverse  is  true. 
A  recent  examination  of  a  lunar  photograph  taken  at  the  Yerkes  Observatory  by 
Professor  Ritchey  has  shown,  however,  that  the  terrestrial  type  of  volcano  is  not 
wholly  absent  from  the  Moon.  Craters  of  this  type  have  not  been  found  before, 
merely  because,  like  those  on  the  Earth,  they  are  very  small.  Figure  6  represents 
the  two  craters  Kies  and  Mercator.  Between  them  is  seen  a  comparatively  small 
cone  with  a  minute  crater  upon  its  summit.  It  proves  to  be  nine  miles  in  diameter 
at  its  base,  and  2000  feet  in  height,  while  the  crater  itself  measures  half  a  mile  in 
diameter.  For  purposes  of  comparison  we  may  say  that  the  diameter  of  the  base 
of  Vesuvius,  including  Monte  Somma,  is  eight  miles,  and  its  height  4000  feet.  The 
diameter  of  its  crater,  which  varies  with  every  eruption,  rarely  exceeds  one  quarter  of 
a  mile,  and  is  sometimes  but  a  few  hundred  feet.  The  mean  angle  of  the  slope  of  Vesu- 
vius is  10.7,  that  of  Etna  7.6,  of  Mauna  Loa  5.1,  and  of  the  lunar  cone  4.8.  Vesuvius 
is  partly  a  lava  and  partly  a  cinder  cone,  which  accounts  for  its  steepness.  If  it  were 


PICKERING. — LUNAR  AND   HAWAIIAN  PHYSICAL   FEATURES   COMPARED.  157 

purely  a  cinder  cone  its  angle  might  rise  to  20°  or  even  30°.  Etna  and  Mauna  Loa 
are  both  lava  cones,  the  lava  of  the  latter  being  more  fusible.  We  may  infer  that  the 
lunar  cone  is  composed  of  similar  material.  It  is  probable  that  other  similar  lava 
cones  exist  upon  the  Moon,  and  one  is  suspected  lying  six-tenths  way  from  Copernicus 
to  Kepler,  and  a  little  to  the  north. 

Lunar  photographs  are  usually  oriented  with  south  at  the  top.  The  right  hand 
side  is  called  east.  Figures  14,  15,  31,  and  35  were  taken  with  a  telescope  of  long 
focus,  using  an  aperture  of  six  inches,  at  the  Harvard  Station  in  the  Island  of 
Jamaica.  The  remaining  lunar  photographs  were  copied  from  lantern  slides  from 
photographs  made  by  Professor  Bitchey  at  the  Yerkes  Observatory.  In  Figure  5,  one 
diameter  to  the  south,  and  a  little  to  the  east  of  Bullialdus  is  a  pair  of  coneless  lava  pits, 
the  southwestern  one  being  much  the  larger  of  the  two.  A  few  other  very  minute  pits 
are  shown  upon  the  photograph,  but  all  the  larger  ones  have  cones.  In  Figure  29,  in 
the  upper  left-hand  corner,  five  small  craters  are  shown  in  a  line  running  north  and  south. 
The  northern  one,  which  is  also  the  smallest,  is  coneless.  One  slightly  larger  than  this, 
also  coneless,  is  shown  just  above  the  centre  of  the  picture,  on  the  southern  side  of  the 
great  rill.  It  measures  five  miles  in  diameter.  These  seem  to  be  true  engulfment  cra- 
ters, as  distinguished  from  the  expulsion  craters  hitherto  described.  Similar  lava  pits 
are  found  to  the  west  and  northwest  of  Copernicus,  and  also  upon  the  Oceanus  Pro- 
cellarum.  In  general  they  are  very  minute  objects.  No  large  crater  pits  are  known. 

In  Figure   7  we  have  a  small  terrestrial  crater  of  this  type.     It  is  known  as 
Kauhaku,  and  is  found  on  the  island  of  Molokai.     It  has  no  exterior  cone  whatever, 
and  is  merely  a  hole  in  the  ground.     Even  explosive  craters  start  in  this  form,  the 
cone  being  formed  immediately  of  materials  ejected  from  the  hole.     Coneless  engulf- 
ment craters  abound  on  the  slopes  of  Hualalai.     See  k,  /,  m,  and/?,  p.  171.     Many 
are  also  found  to  the  southeast  and  east  of  Kilauea,  but  the  best  known  of  all  is 
Halemaumau,  on  the  floor  of  Kilauea  itself,  dt  p.  171.     Figure  8  is  known  as  Kuuohi, 
or  more  familiarly  as  the  sixth  crater,  and  is  situated  six  miles  to  the  southeast  of 
Kilauea.     See  also/,  p.  171.     The  floor  of  the  main  crater  pit  measures  about  6,00( 
feet  in  length  by  2,000  in  breadth.     Its  depth  below  the  surrounding  surface  is 
feet.     At  its  eastern  end  a  second  crater  pit  has  formed.    This  measures  2,00( 
in  diameter,  and  has  an  additional  depth  of  600  feet.     It  furnishes  a  vertical 
150  feet  in  depth  of  the  primary  floor,  below  which  the  walls  form  an  inverte 
cated  cone  to  a  small  floor  a  few  hundred  feet  in  diameter.     The  lava  of  the  uppe: 
twenty-five  feet  of  the  vertical  section  has  a  horizontal  stratification,  and 
distinguished  from  the  portion  below  it. 


158  PICKERJNG. LUNAK   AND    HAWAIIAN   PHYSICAL    FEATURES    COMPARED. 

Of  the  three  great  Hawaiian  representatives  of  the  engulfment  type,  Mokuaweoweo, 
the  summit  crater  of  Mauna  Loa,  Figure  9,  and  Kilauea,  Figure  10,  are  coneless,  while 
Haleakala,  Figure  3,  has  in  places  a  well-defined  outer  slope.  This  might  lead  us  to 
suspect  that  it  was  of  composite  origin,  an  impression  that  is  further  confirmed  by  the 
fact  that  both  its  inner  and  outer  slopes  are  made  up  in  part  of  lava,  and  in  part 
of  scoria  and  sand.  It  seems  to  have  originated  partly  by  the  engulfment  process  and 
partly  by  explosions  of  steam. 

No  evidence  of  the  great  crater  of  Mokuaweoweo  is  to  be  seen  until  just  before  we 
reach  its  rim.  It  measures  3.7  by  1.7  miles  in  diameter,  and  is  300  to  400  feet  in 
depth.  It  is  composed  of  three  confluent  craters,  of  which  the  middle  one  is  much 
the  largest.  A  portion  of  the  two  northern  ones  is  shown  in  the  figure,  the  view 
being  taken  in  a  direction  nearly  due  south.  The  crater  floor  corresponds  very 
closely  in  its  nature  to  a  lunar  mare. 

Kilauea  is  much  more  accessible  than  Mokuaweoweo.  Twenty-two  miles  in  the 
train  from  Hilo,  and  nine  miles  by  stage  brings  us  to  the  Volcano  House,  situated 
upon  its  brink.  Kilauea  consists  of  a  black  lava  plain  measuring  two  miles  by 
three,  bounded  on  all  sides  by  precipices,  often  vertical,  ranging  from  200  to  500  feet 
in  height.  The  view,  Figure  10,  was  taken  from  its  southeastern  rim  looking  north. 
It  is  a  curious  fact  that  the  black  lava  usually  shows  in  the  photographs  to  be  much 
lighter  colored  than  the  gray  cliffs  surrounding  it.  Since  the  whole  lava  surface  is 
very  irregular,  the  fact  that  it  is  shiny  and  therefore  bright  in  spots,  cannot  be  given 
as  an  explanation  of  this  fact.  The  surface  is  distinctly  convex,  d  p.  171,  as  is  the 
case  with  the  smooth  crater  floors  upon  the  Moon,  and  is  not  unlike  in  shape  and 
curvature  to  the  flattened  summit  of  Mauna  Loa,  Figure  4.  A  in  the  section 
indicates  the  location  of  the  Volcano  House.  The  line  B  is  on  a  level  with  it.  The 
highest  part  of  the  floor,  is  near  Halemaumau,  and  in  1905  measured  230  feet  above 
the  edge  where  the  Volcano  House  trail  strikes  it.  The  edge  is  410  feet  below 
the  Volcano  House  at  this  point. 

Halemaumau,  "  the  house  of  eternal  fire,"  is  situated  three-quarters  way  across  the 
crater  from  the  Volcano  House.  It  is  at  present  a  nearly  circular  pit,  2,000  feet  in 
diameter,  with  practically  vertical  sides,  and  when  the  writer  was  there  early  in 
August  its  depth  was  estimated  at  500  feet.  Its  floor  consisted  of  a  comparatively 
smooth  lava  surface,  crossed  here  and  there  by  narrow  cracks,  which  at  night  showed 
bright  red.  That  it  was  liquid  only  a  few  inches  below  the  surface  was  shown  by  an 
occasional  outbreak,  when  a  flow  of  lava  5  to  10  feet  broad  by  20  to  50  feet  in  length 
would  sluggishly  stretch  itself  across  the  floor,  glow  for  a  few  minutes,  and  then  cool 


PICKERING.  — LUNAR  AND   HAWAIIAN    PHYSICAL   FEATURES   COMPARED.  159 

and  solidify.  From  a  height  of  500  feet  the  phenomenon  presented  little  of  interest 
compared  to  what  had  been  seen  in  the  last  century.  The  crater  is  gradually  filling 
up  from  a  subterranean  inlet.  The  depth  of  the  pit  in  1902  was  estimated  at  1,000 
feet.  The  lower  portion,  which  has  now  been  filled  was  then  conical  in  shape. 

Turning  now  to  the  third  subdivision  of  the  lava  craters,  the  crater  rings,  we  will 
begin  by  a  study  of  what  is  believed  to  be  their  internal  structure,  as  exhibited  in 
Figure  11.  This  photograph  represents  a  vertical  section  of  a  small  ring  crater  formed 
naturally  in  cooling  iron  slag.  When  the  slag  is  drawn  off  from  the  furnace  it  is 
allowed  to  solidify  in  conical  moulds  four  or  five  feet  in  diameter,  and  about  a  foot  in 
depth  at  the  centre.  Unless  interfered  with,  a  crater  three  or  four  inches  in  diameter 
is  invariably  formed  as  soon  as  the  surface  has  fairly  hardened.  On  breaking  up  the 
slag  considerable  cavities  are  always  found  beneath  the  crater.  These  are  well  shown 
in  the  figure,  as  are  also  the  cracks  connecting  them  with  one  another  and  with  the 
central  peak,  which  it  will  be  noted  is  also  hollow.  The  large  pear-shaped  cavity 
beneath  the  peak  was  in  the  present  instance  filled  up  from  below  with  melted  iron. 
It  will  be  noted  that  the  inner  walls  are  very  steep,  while  the  outer  ones  slope  more 
gradually.  During  the  process  of  formation  the  crater  sometimes  fills  to  the  brim 
and  overflows,  building  up  the  walls ;  later  the  interior  fluid  withdraws,  forming  the 
crater  floor. 

Besides  these  larger  craters  other  ones  are  often  formed,  which,  while  retaining  a 
base  of  perhaps  two  inches  in  diameter,  frequently  build  up  to  the  height  of  several 
inches,  forming  vertical  tubes  or  spiracles.  Sometimes  these  tubes  are  closed  at  the 
top  and  sometimes  they  are  left  open.  For  these  facts,  and  for  the  specimen  from 
which  Figure  11  is  taken,  I  am  indebted  to  Mr.  J.  A.  Brashear. 

Halemaumau,  known  also  as  "  the  pit,"  is  the  centre  of  volcanic  activity  in  Kilauea. 
No  eruption  has  ever  been  known  to  overflow  the  walls  of  the  latter,  although  lava 
has  sometimes  been  emitted  from  cracks  located  high  up  on  its  sides.  When  the  pit 
of  Halemaumau  is  emptied,  it  is  always  through  some  subterranean  passage,  occasion- 
ally reaching  the  surface,  but  usually  either  filling  some  subterranean  cavity,  or  else 
discharging  beneath  the  sea.  These  eruptions,  though  often  accompanied  by  slight 
earthquake  shocks,  have  in  only  one  instance  caused  serious  damage  and  loss  of  life. 
In  this  case  it  is  thought  that  the  active  agency  was  really  Mauna  Loa,  whose  erup- 
•  tion  took  place  at  the  same  time. 

When  Halemaumau  is  really  active  the  sight  is  said  to  be  grand  beyond  description, 
especially  at  night.  Lakes  of  liquid  lava  occur  both  within  and  without  it.  Numer- 
ous fire  fountains  from  ten  to  fifty  feet  in  height  play  over  the  surface  of  these  lakes. 


160  PICKERING. LUNAR   AND    HAWAIIAN    PHYSICAL   FEATURES    COMPARED. 

At  times  the  surface  solidifies,  then  suddenly  a  crack  will  run  across  it,  and  in  a 
few  minutes  the  whole  solid  material  will  break  up  into  separate  cakes  which  will 
presently  turn  on  edge  and  sink  beneath  the  surface  of  the  lake.  This  again  solidifies, 
and  in  a  few  hours  the  process  is  repeated.  See  report  of  the  United  States  Geo- 
logical Survey  for  1883,  p.  106,  Major  C.  E.  Button. 

These  lakes  are  especially  interesting  to  the  selenographer,  since  about  them  are 
formed  crater  rings,  which  seem  to  be  analogous  in  appearance  to  the  larger  crater 
formations  upon  the  Moon.  During  the  past  forty  years,  since  the  construction  of  the 
hotel  upon  the  rim  of  Kilauea,  they  have  been  very  carefully  observed,  and  it  will 
therefore  be  well  in  this  place  to  deal  with  the  subject,  briefly,  from  the  chronological 
standpoint.  All  the  earlier  descriptions  which  follow  are  condensed  from  the  writings 
of  the  Rev.  Titus  Coan.  The  references  given  refer  to  the  American  Journal  of 
Science. 

On  April  2,  1868,  a  severe  earthquake  shook  the  southern  coast  of  Hawaii,  and 
for  the  next  five  days  a  subterranean  discharge  of  lava  took  place  from  Kilauea.  As 
a  result  of  this  discharge  the  central  area  to  the  northeast  of  Halemaumau  sank  about 
300  feet,  carrying  with  it  the  vegetation  still  growing  on  its  surface.  The  walls  of 
this  new  pit  were  inclined  from  30°  to  60°.  The  lava  also  flowed  out  of  Halemaumau, 
leaving  a  circular  pit  3000  feet  in  diameter  at  the  top,  1500  feet  at  the  bottom,  and 
500  feet  deep.  Its  walls  were  in  some  places  vertical,  and  in  some  slightly  over- 
hanging. A.  J.  S.,  XCVII,  96.  •  In  A.  J.  S.,  CXVIII,  227,  it  is  stated  that  the 
depth  was  400  feet  and  that  the  distance  across  the  bottom  was  one  mile  less  one 
hundred  feet.  It  is  also  stated  that  the  pit  had  formerly  been  filled  up  not  only  from 
the  bottom,  but  by  lateral  discharges  from  the  walls. 

A  year  later  Halemaumau  had  filled  to  within  100  feet  of  the  top,  the  level  area 
within  it  showing  eight  small  apertures  within  which  the  liquid  lava  could  be  seen 
boiling  fiercely  50  to  100  feet  below  the  surface.  A  few  months  later  the  lava  was 
within  25  feet  of  the  rim,  and  the  diameter  of  the  pit  was  said  to  have  enlarged  to 
over  a  mile.  A.  J.  S.,  XCIX,  393. 

In  1870  the  pit  overflowed,  the  lava  pouring  down  and  partly  filling  the  north- 
eastern depression.  At  the  time  of  an  eruption  such  as  this,  the  lava  rises,  overflows 
and  cools,  thus  forming  a  raised  rim  or  circular  dam.  Such  a  rim  is  shown  on  a 
small  scale  in  the  slag  crater,  Figure  11,  and  on  a  much  larger  scale  in  the  photo- 
graphs of  Halemaumau,  Figures  12  and  13,  the  cakes  of  lava  there  represented 
appearing  much  like  broken  cakes  of  ice.  In  Figure  14  is  shown  a  portion  of  the 
Moon  near  the  limb,  so  as  to  present  the  craters  obliquely.  It  will  be  noted  that  the 


PICKERING.  — LUNAR   AND   HAWAIIAN   PHYSICAL   FEATURES   COMPARED.  161 

two  large  craters  there  represented,  named  Schickard  and  Phocylides,  both  present  a 
form  similar  to  the  crater  rings  of  Halemaumau.  The  chief  one,  Schickard,  measures 
134  miles  in  diameter.  All  of  the  larger  craters  on  the  Moon  are  of  this  type. 
When  seen  towards  the  centre  of  the  disc,  however,  their  depth  appears  by  an  optical 
illusion  greatly  exaggerated.  Thus  Clavius,  the  largest  crater  shown  in  Figure  16 
measures  143  miles  in  diameter,  and  judging  by  appearances  only  might  be  15  to  20 
miles  in  depth.  Its  depth  actually  measures  two  and  a  half  miles,  or  about  the  same 
as  the  diameter  of  one  of  the  most  minute  craterlets  visible  in  its  interior.  The  slope 
of  its  eastern  inner  wall  is  about  10°. 

There  is  another  crater  known  as  Wargentin,  lying  between  Schickard  and  - 
Phocylides  and  the  limb,  Figure  14.  It  is  not  shown  in  the  photograph  because  it  is 
a  very  difficult  object.  This  is  not  on  account  of  its  size,  since  it  measures  fifty-four 
miles  in  diameter,  but  because  it  has  no  interior  depression.  In  this  respect  it  has 
heretofore  been  thought  to  be  unique  upon  the  Moon.  That  such  is  not  the  case, 
however,  an  inspection  of  Figure  32  will  show.  Near  the  upper  edge  of  the  figure 
a  large  low  nameless  crater  is  to  be  seen  whose  interior  is  obviously  at  a  greater 
elevation  than  its  exterior,  although  the  difference  is  not  as  great  as  in  the  case  of 
Wargentin.  It  measures  about 'fifteen  miles  in  diameter.  In  each  of  these  cases 
the  lava  passage  leading  to  the  interior  of  the  crater  evidently  became  choked  while 
the  crater  was  still  brimful  of  molten  matter,  thus  preventing  the  withdrawal  of  the 
lava,  and  preserving  the  crater  as  a  permanent  illustration  of  the  method  by  which 
these  formations  are  produced. 

The  outside  height  of  the  crater  rings  in  Halemaumau  rarely  exceeds  15  to  25  feet. 
The  inside  height  is  constantly  varying  with  the  fluctuating  level  of  the  surface 
of  the  lava  lake.  When  the  outside  height  becomes  too  great  to  withstand  the 
internal  pressure,  the  rim  gives  way,  and  the  lava  breaks  through  and  floods  the 
surrounding  regions.  By  means  of  this  successive  building  up  and  flooding,  the  whole 
region  around  Halemaumau  was  elevated,  until  the  walls  became  too  high  and  too 
thick  for  the  floods  to  escape  over  or  through  them.  The  pit  at  this  time  measured  a 
mile  by  a  mile  and  a  half,  and  was  700  feet  in  depth.  Since  the  lava  could  not 
now  overflow  the  rim,  it  escaped  by  subterranean  passages,  and  thus  flooded  the 
other  portions  of  the  floor  of  Kilauea.  A.  J.  S.,  CII,  454. 

It  is  doubtful  if  the  walls  of  the  pit  were  raised  exclusively  by  the  process  thus 
explained  by  Mr.  Coan.  It  is  probable  that  the  whole  of  this  portion  of  the  floor 
was  also  elevated  as  one  piece  by  the  pressure  of  the  subterranean  lava,  as  occurred 

in  the  later  eruptions. 

11 


162  PICKERING. —  LUNAR  AND   HAWAIIAN   PHYSICAL    FEATURES    COMPARED. 

On  the  Moon  the  height  of  the  outer  wall  is  roughly  proportional  to  the  diameter 
of  the  crater.  For  a  crater  whose  diameter  measures  30  to  40  miles,  the  height 
of  the  outer  wall  is  usually  about  one  mile.  For  a  crater  a  mile  in  diameter  its 
height  would  be  150  feet.  Dividing  this  figure  by  6,  the  correction  for  gravity 
mentioned  at  the  beginning  of  this  paper,  we  find  25  feet  to  be  the  theoretical 
height  for  a  terrestrial  crater  a  mile  in  diameter,  thus  agreeing  with  the  figure 
above  given. 

In  April,  1879  a  silent  discharge  from  the  crater  occurred,  the  lava  apparently 
making  its  escape  out  at  sea.  A  few  months  later  activity  was  again  resumed,  the 
crater  becoming  extremely  active  in  1880.  A.  J.  S.,  CXVIII,  227 ;  CXX,  72. 

On  March  6,  1886,  Halemaumau  was  again  emptied.  It  was  a  silent  discharge 
like  its  predecessor.  For  several  days  the  surrounding  walls  continued  to  fall  into 
the  pit.  A  month  later  the  deepest  portion  had  the  shape  of  an  inverted  cone, 
whose  apex  was  570  feet  below  the  floor  of  Kilauea.  Three  months  after  an  erect 
cone  was  found  formed  of  loose  blocks,  and  measuring  150  feet  in  height.  During 
the  next  two  years  this  cone  gradually  floated  upwards,  no  additions  being  made 
to  its  summit.  This  action  seems  to  have  been  due  to  the  pressure  of  the  lava 
beneath  it.  The  rate  of  elevation  was  about  three  inches  per  day.  A.  J.  S.,  CXXXI, 
397;  CXXXVII,  48. 

The  next  discharge  of  Halemaumau  occurred  on  March  6,  1891.  It  was  accom- 
panied and  followed  by  a  series  of  light  earthquake  shocks,  but  otherwise  it  was  a 
quiet  discharge.  Prior  to  this  date  the  pit  contained  a  central  cone  with  three  lakes 
surrounding  it,  one  east,  one  west,  and  one  south.  The  direction  of  the  current  on 
the  surface  of  these  lakes  in  each  case  was  away  from  the  cone.  The  cone  which  con- 
sisted in  part  of  several  peaks  rose  to  a  height  of  at  least  200  feet  above  the  lakes. 
As'seen  from  the  Volcano  House  about  one-third  of  its  height  was  above  the  western  wall 
of  Kilauea.  The  structure  of  these  peaks  was  loose,  and  sulphurous  vapors  escaped 
from  their  whole  surface.  The  fire  fountains  on  the  lakes  sometimes  played  obliquely, 
and  without  the  emission  of  steam.  On  the  evening  of  March  6,  at  9:30,  a  light  earth- 
quake shock  was  felt,  and  the  peaks  settled  slightly ;  the  next  morning  they  were  out 
of  sight.  A  month  later  in  place  of  the  peaks  and  lakes  an  empty  pit  was  seen, 
measuring  half  a  mile  in  diameter.  The  walls  were  vertical  and  500  feet  in  depth. 
Soon  after  this  the  lava  reappeared  in  the  bottom  of  the  pit,  and  by  the  end  of  April 
a  lava  lake  100  to  200  feet  in  diameter  had  formed.  A  year  later  the  diameter  of 
the  lake  was  a  little  over  800  feet.  It  was  then  very  active,  as  many  as  fifteen  fire 
fountains  having  been  counted  at  one  time.  It  was  probably  at  about  this  time  that 


PICKERING.- 


LUNAR  AND   HAWAIIAN   PHYSICAL  FEATURES   COMPARED. 


163 

the  photographs  shown  in  Figures  12  and  13  were  taken.  A.  J.  S.,  CXLI  336  507  • 
CXLII,77;  CXLV,241. 

The  next  discharge  was  on  July  11,  1894.    In  August,  1892,  the  edge  of  the  pit 
Halemaumau  was  282  feet  below  the  level  of  the  Volcano  House.     The  surface  of 

the  lake  was  240  feet  below  the  edge,  522  feet 
in  all.  (See  cut.)  In  March,  1894,  the  surface 
of  the  lake  was  75  feet  below  the  Volcano 
House,  making  a  total  rise  of  447  feet  in  nine- 
teen months,  or  about  ten  inches  per  day.  In 
1892  the  lake  was  in  the  bottom  of  the  pit. 

In  1894  the  pit  was  filled,  and  the  lake  was  on  the  top  of  a  flat  hill  covering  the  pit 
and  situated  207  feet  above  its  former  rim.  The  pit  was  filled  partly  by  overflows  from 
the  lake,  and  partly  by  a  rise  of  the  whole  bottom  of  the  pit.  The  lake  now  measured 
800  by  1200  feet. 

On  March  21  an  area  measuring  400  by  800  feet,  situated  on  the  northern  bank  of 
the  lake,  was  suddenly  elevated  eighty  feet  above  the  other  banks.  The  raised  area 
was  much  shattered.  It  subsequently  sank  gradually,  until  on  July  11  it  again 
reached  its  former  level.  On  that  date  the  lava  in  the  lake  began  rapidly  to  sink, 
and  the  walls  about  the  lake  to  crack  off  and  fall  into  it.  The  lava  sank  at  the  rate 
of  twenty  feet  an  hour  until  eight  that  evening.  From  noon  till  eight  there  was 
scarcely  a  moment  when  the  crash  of  the  falling  blocks  was  not  heard.  A  number  of 
times  a  section  200  to  500  feet  long,  100  to  200  feet  high,  and  20  to  30  feet  thick 
would  drop  with  a  tremendous  roar  into  the  boiling  lava.  Such  a  section  would  form 
for  a  time  a  floating  island  in  the  lake,  but  would  subsequently  dissolve  and  sink. 
The  grandeur  and  magnificence  of  the  scene  at  night  were  indescribable.  Meanwhile 
the  fountains  in  the  lake  continued  to  play  as  if  nothing  unusual  were  happening.  Only 
a  few  slight  earthquakes  accompanied  this  discharge.  A.  J.  S.,  CXLVIII,  338. 

Since  this  time  for  an  interval  of  over  twelve  years  the  volcanic  forces  in  Kilauea  have 
been  practically  quiescent.  There  was  a  slight  display  of  activity  in  1896,  and  again  in 
1897,  but  the  pit  remained  empty,  and  no  activity  whatever  has  been  seen  since  then, 
except  for  the  gradual  and  uneventful  filling  of  the  pit  which  seems  now  to  be  taking 
place.  No  such  protracted  interval  of  quiet  has  been  known  heretofore,  the  longest  pre- 
vious period  amounting  to  only  a  few  months.  It  is  of  interest  to  note  that  of  the  five 
recorded  discharges,  four  occurred  during  the  rainy  months  of  March  and  April. 

From  these  descriptions  we  can  obtain  an  idea  of  how  the  lunar  craters  were 
formed,  and  can  also  account  for  the  flat-topped  vertical  cliffs  that  we  find  about 


164  PICKERING.  —  LUNAR   AND   HAWAIIAN    PHYSICAL    FEATURES    COMPARED. 

some  of  the  maria,  as  in  the  case  of  Sinus  Iridum,  Figure  15.  The  walls  of  Mokuaweo- 
weo  or  of  Kilauea,  Figures  9  and  10,  furnish  excellent  illustrations  of  these  forma- 
tions. Examples  of  the  crater  rings  themselves,  however,  are  rare.  The  best  preserved 
one  that  we  were  able  to  visit  was  found  on  Hualalai,  at  an  elevation  of  400  feet 
below  the  summit  of  the  mountain,  and  was  reached  a  few  minutes  after  passing  the 
so-called  Bottomless  Pit.  It  was  located  on  the  floor  of  a  crater  some  500  feet  in 
diameter  by  100  feet  in  depth,  g  p.  171.  The  diameter  of  the  crater  ring  was  120 
feet,  its  internal  depth  was  six  feet  and  the  height  of  its  outside  wall  twelve  to  sixteen 
feet.  It  is  shown  upon  a  larger  scale  at  h  p.  171.  Near  the  centre  of  the  outer  crater, 
and  outside  of  the  crater  ring,  was  a  low  peak.  What  appeared  to  be  another  crater 
ring  was  seen  from  the  distance  of  a  mile  on  the  northern  slopes  of  Mauna  Loa,  and 
will  be  described  later.  A  portion  of  one  of  the  crater  rings  formed  by  Halemaumau 
is  still  to  be  seen  on  the  rim  near  the  view-point  where  visitors  look  down  into  the 
interior. 

The  reason  that  these  crater  rings  are  so  numerous  upon  the  Moon  and  so  rare 
upon  the  Earth  is  apparently  that  the  terrestrial  ones  are  not  generally  permanent. 
The  smaller  craters  on  the  Moon  do  not  take  this  form,  and  if  some  of  them  did  exist 
formerly  they  have  since  been  destroyed.  The  reason  of  this  is  that  when  the  lava 
recedes  into  the  bottom  of  the  pit,  the  depth  is  so  great  in  proportion  to  the  diameter, 
that  the  walls  cave  in,  destroying  the  ring,  —  as  usually  happens  at  Halemaumau. 
On  the  Moon  no  crater  is  known  whose  depth  exceeds  five  miles,  and  two  miles  is  the 
usual  depth  for  large  craters.  This  distance  compared  to  a  diameter  of  twenty  to 
sixty  miles  is,  so  slight  that  the  ring  remains  uninjured.  The  outer  walls  of  Haleakala 
may  in  part  be  the  remains  of  an  old  crater  ring  of  very  elliptical  shape.  They  have 
been  breached  and  totally  destroyed  in  two  places. 

The  floors  of  the  craters  on  the  Moon  are  of  three  kinds,  either  they  are  furnished 
with  a  central  peak,  like  Tycho,  the  large  crater  in  the  lower  left  hand  corner  of 
Figure  16,  or  they  contain  one  or  more  smaller  craters,  in  general  not  central,  like 
Clavins,  in  the  same  figure ;  or  they  are  without  conspicuous  detail,  like  Kies,  Figure 
6.  In  the  last  two  cases  the  floor  is  often  of  a  later  origin  than  the  walls,  as  indicated 
by  its  color  and  smoothness,  the  original  floor  having  been  melted  by  a  flood  of  dark 
colored  lava  from  below,  which  dissolved  all  the  lowermost  portions  of  the  solid  crust 
with  which  it  carne  in  contact.  This  seems  to  be  the  case  with  Longomontanus,  the 
large  crater  northeast  of  Clavius.  Its  diameter  is  ninety-one  miles.  Often,  however, 
the  floor  is  bright,  and  not  perfectly  smooth,  as  in  Tycho,  showing  it  to  be  part  of  the 
original  formation.  Central  peaks  are  occasionally,  but  by  no  means  universally, 


PICKERING.  — LUNAR  AND    HAWAIIAN    PHYSICAL  FEATURES   COMPARED.  165 

found  upon  these  original  floors.  Indeed  they  rarely  occur  in  craters  of  less  than 
Four  miles  in  diameter.  Longomontanus  and  another  crater  known  as  Pitatus  present 
the  very  unusual  phenomena  of  eccentric  internal  peaks.  Equally  striking  is  the  fact 
that  in  each  case  the  peak  is  found  in  connection  with  a  dark  floor.  The  explanation 
in  both  cases  is  probably  that  the  lava,  after  dissolving  the  original  floor,  had  begun 
to  dissolve  the  peaks,  which  were  pushed  by  the  lava  currents  to  one  side,  where 
cooling  and  solidification  set  in  before  the  process  was  completed.  In  both  these 
cases  the  peaks  are  unusually  small  in  proportion  to  the  size  of  the  craters,  as  would 
naturally  be  the  case  if  they  had  been  floating  partially  submerged  in  the  lava. 

Central  peaks  are  seldom  found  in  the  Hawaiian  craters,  probably  because  the 
latter  are  so  small.  The  best  illustration  seen  was  that  of  the  small  crater  already 
mentioned  at  the  northern  base  of  Mauna  Loa,  about  eight  miles  west  of  the  Humuula 
sheep  ranch,  i  p.  171.  Unfortunately  we  could  not  get  within  a  mile  of  it,  but  it 
seemed  to  be  well  defined.  Its  diameter  was  thought  to  be  about  450  feet.  The 
walls  were  red,  and  the  central  peak  dark  brown.  The  height  of  the  peak  was  the 
same  as  that  of  the  walls.  Another  small  crater  two  or  three  hundred  yards  back 
of  Mr.  Maguire's  at  Huehue  in  Kona  showed  a  smooth  central  peak  15  feet  in  height. 
It  was  completely  grass  grown.  'One  or  two  of  the  small  craters  on  Hualalai, 
k  p.  171,  showed  the  same  formation.  The  peaks  were  never  pointed,  but  sandy  and 
rounded  as  in  the  slag  crater  shown  in  Figure  11.  A  crater  containing  a  central 
peak  or  craterlet  is  said  'to  exist  half  a  mile  beyond  the  sixth  crater  near  Kilauea. 
Near  the  centre  of  Haleakala  is  found  a  straight,  narrow  ridge,  150  feet  in  height  by 
400  feet  in  length,  along  its  crest.  Its  sides  slope  at  an  angle  of  about  30°  and  it  is 
composed  apparently  of  gravel  and  scoria.  At  its  eastern  base  is  the  cave  where 
parties  sometimes  pass  the  night.  Although  not  especially  conspicuous  among  the 
crater  cones  which  dot  the  floor,  some  of  which  are  500  feet  in  height  (see  Figure  3), 
it  seems  to  be  unique  in  shape,  running  lengthwise  of  the  crater.  It  is  also  almost 
exactly  central  in  position.  In  passing  it  may  be  stated  that  the  maps  of  Haleakala 
give  a  very  erroneous  impression  of  the  shape  of  its  floor.  The  floor  at  the  Koolau 
and  Kaupo  gaps  falls  off  sharply,  showing  the  outline  of  the  true  floor  to  be  not 
S-shaped,  but  elliptical,  and  extending  nearly  due  east  and  west.  It  is  an  ellipse 
of  great  eccentricity,  the  length  of  the  floor  being  about  four  times  its  breadth. 

Figure  18  represents  a  portion  of  the  middle  crater  of  Mokuaweoweo.  Somewhat 
nearer  than  the  centre  is  shown  an  active  cinder  cone  composed  apparently  of  a 
medium-sized  crater  and  two  or  three  smaller  ones  upon  its  rim.  We  were  not  able 
to  visit  it.  Like  the  craterlets  found  in  Haleakala,  it  reminds  us  of  those  found  in 


166  PICKERING.  —  LUNAR   AND    HAWAIIAN    PHYSICAL    FEATURES    COMPARED. 

Clavius.  The  photograph  was  taken  in  1903  by  Mr.  C.  W.  Baldwin,  and  was 
forwarded  to  me  through  the  kindness  of  Professor  W.  D.  Alexander. 

One  of  the  most  interesting  craters  that  we  visited  was  Kilauea  Iki,  or  little 
Kilauea.  It  is  situated  about  a  mile  from  the  Volcano  House.  The  floor  is  level, 
one-quarter  of  a  mile  in  diameter  and  750  feet  below  the  rim.  The  walls  are  very 
steep,  but  can  be  descended  in  certain  places  with  care.  Numerous  small  craterlets 
are  scattered  irregularly  over  the  floor.  The  most  complete  of  these  is  shown  in 
Figure  19.  Its  height  was  15  feet,  and  the  diameter  of  the  rim,  which  was  composed 
of  lava  of  a  somewhat  ropy  appearance,  25  feet.  A  stream  of  lava  had  poured  from 
the  summit,  but  did  not  get  far  beyond  the  rim.  There  may  have  been  as  many  as 
fifty  rudimentary  craterlets  scattered  over  the  floor,  in  all  stages  of  growth,  from 
a  hardly  noticeable  elevation  to  the  complete  craterlet  shown  in  the  figure. 

The  process  of  construction  was  clearly  shown,  and  was  probably  identical  with 
that  which  produced  Halemaumau,  and  Kilauea  itself  in  the  first  place.  In  Figure  20 
the  top  of  one  of  the  other  craterlets  is  represented  in  the  foreground.  It  was  taken 
near  at  hand  from  the  summit  of  the  first  one,  and  its  development  is  clearly  incom- 
plete. The  surface  of  the  crater  floor  of  Kilauea  Iki  seems  to  have  solidified  into 
a  layer  six  to  ten  inches  in  depth  and  distinct  from  the  portions  below  it,  much  as  in 
the  case  of  the  sixth  crater,  Figure  8.  A  liquid  core  forced  up  from  below  raised 
this  surface  layer  locally,  and  shattered  it  into  separate  pieces  like  cakes  of  ice. 
This  core  in  the  case  of  some  of  the  smaller  craterlets  was  sometimes  only  two  or 
three  feet  in  diameter,  and  could  be  seen  beneath  the  shattered  surface.  In  one 
instance  its  summit  seemed  to  have  an  almost  globular  form,  five  feet  in  diameter. 

If  the  volcanic  forces  beneath  these  craterlets  had  been  more  intense,  it  is  probable 
that  the  issuing  lava  would  have  completely  destroyed  them,  forming  a  series  of 
crater  pits,  into  which  the  lava  would  have  subsequently  retreated.  In  the  south- 
eastern part  of  the  floor  two  such  pits  were  found,  perhaps  15  feet  in  depth  by 
30  in  diameter,  down  into  which  a  stream  of  lava  had  poured,  but  had  solidified 
without  filling  them  up.  One  of  these  pits  is  shown  in  Figure  21.  Figures  20 
and  19  therefore  illustrate  the  earliest  stages  of  formation  of  a  lunar  crater.  No 
other  example  in  Hawaii  is  known  to  the  writer  which  shows  as  satisfactorily  as  this 
the  irregular  distribution  of  craterlets  over  a  crater  floor. 

A  low  ridge  due  to  compression,  caused  by  the  sinking  of  the  convex  surface 
crosses  the  eastern  end  of  the  crater  floor.  Similar  ridges  are  seen  on  some  of  the  lunar 
maria,  notably  on  Serenitatis,  Figure  17.  Two  short,  clearly  marked  ridges  project 
onto  the  southern  side  of  the  floor  of  Kilauea  Iki,  caused  by  lava  streams  which  had 


PICKERING.  — LUNAR   AND    HAWAIIAN   PHYSICAL   FEATURES   COMPARED.  167 

descended  from  the  crater  wall.  They  resemble  similarly  located  formations  found 
in  the  lunar  crater  Plato.  In  Clavius,  Figure  16,  similar  ridges  are  seen  projecting 
from  the  outer  slopes  of  the  two  chief  craterlets  upon  the  northern  and  southern 
walls.  Similar  ridges,  although  much  more  complicated  in  structure  ou  account 
of  their  numbers,  have  already  been  described  in  Bullialdus,  Figure  5. 

Leaving  the  craterlets  and  ridges  of  Kilauea  Iki,  and  proceeding  along  a  defile 
towards  Kilauea  itself,  three  successive  lava  dams  were  reached,  each  of  which  had 
served  to  hold  back  a  small  lava  lake.  In  construction  they  were  similar  to  the 
circular  one  represented  in  Figure  12,  except  that  they  were  straight,  and  merely 
stretched  across  the  defile.  The  first  lake  measured  400  feet  in  length  by  150  in 
breadth.  The  second  dam  rose  eight  feet  above  its  surface,  and  three  feet  above 
that  of  the  second  lake.  By  the  side  of  this  lake  a  core  of  lava  of  the  most  brilliant 
colors  —  red,  yellow,  brown,  and  purple  —  had  escaped  from  the  ground,  and  from  it 
a  black  lava  stream  had  descended  to  the  surface  of  Kilauea  Iki,  200  feet  below. 
A  similar  core  but  without  the  colors  was  seen  at  Huehue.  Both  these  flows  occurred 
during  the  last  century.  Both  were  small,  and  in  neither  case  did  a  cone  appear, 
the  lava  issuing  directly  from  the  ground. 

The  fourth  subdivision  of  the  /lava  craters,  described  earlier  as  crater  bowls,  is 
illustrated  in  Hawaii  by  what  is  known  as  Aloi,  or  the  Third  Crater,  near  Kilauea. 
Other  illustrations  are  found  on  the  slopes  of  Hualalai.  A  crater  near  the  summit, 
j,  p.  171,  was  estimated  at  800  feet  in  diameter  by  200  in  depth.  The  sloping  walls 
were  of  lava,  and  the  bottom  of  sand.  The  comparatively  shelving  outer  walls 
probably  did  not  exceed  100  feet  in  height.  A  portion  of  the  interior  of  this  crater 
is  shown  in  Figure  22.  A  somewhat  larger  crater  bowl  with  much  steeper  walls 
is  found  on  the  summit.  With  favorable  definition  such  a  crater  would  be  readily 
seen  upon  the  Moon,  and  could  not  be  distinguished  in  any  way  from  many  others 
found  there. 

The  largest  craters  on  Hualalai  occurred  near  the  summit,  and  shortly  before 
reaching  the  top  we  crossed  a  lava  field  strongly  resembling  a  small  lunar  mart. 
A  far  larger  number  of  craters  are  found  on  this  mountain  than  on  any  of  the 
others,  more  perhaps  than  on  all  the  others  combined.  The  three  types,  of  cinder 
cones,  pits,  and  bowls,  are  each  represented  by  numerous  examples.  One  of  the 
craters  that  we  passed  after  leaving  the  summit,  k,  p.  171,  had  sloping  walls  and  a  flat 
floor  with  sand  hills  on  the  bottom.  One  of  these  was  twenty  feet  in  height.  Near 
the  base  of  the  walls  was  an  inner  terrace  extending  all  around  the  crater.  This 
feature  of  a  single,  well  marked,  inner  terrace  is  conspicuous  in  a  considerable 


168  PICKERING. LUNAR   AND    HAWAIIAN    PHYSICAL    FEATURES    COMPARED. 

number  of  the  lunar  craters,  such  as  Fabricius,  Hercules,  Manilius,  Reinhold,  and 
Bullialdus  (see  Figure  5). 

Some  of  the  lava  pits  occur  very  near  together,  the  intermediate  wall  being  only 
a  few  yards  in  thickness,  but  we  saw  none  which  actually  intersected.  When  the 
large  summit  crater  was  formed  a  smaller  one  near  it  was  partially  destroyed,  and 
filled  by  the  erupted  material  from  the  larger  crater. 

We  have  no  description  of  the  method  of  formation  of  a  crater  bowl,  but  a  study 
of  the  various  sections  on  p.  171  will  show  how  they  have  probably  been  formed, 
Starting  with  a  crater  ring  such  as  is  shown  in  Figure  19,  and  in  section  at  h,  p.  171, 
when  the  lava  retreats  a  crater  pit  will  be  formed  within  it.  If  the  pit  is  very  deep 
relatively  to  the  diameter  of  the  ring,  the  latter  will  be  destroyed,  and  we  shall 
have  simply  an  ordinary  pit,  I.  If  the  pit  is  not  so  deep  relatively  to  the  diameter 
of  the  rim  the  latter  may  be  preserved,  n.  The  floor  of  the  pit  may  be  flat,  or  it  may 
sink  towards  the  centre,  m.  If  the  pit  is  on  a  large  scale  the  sides  are  less  liable 
to  be  vertical,  and  moreover  a  talus  will  collect  at  their  base,  o.  This  will 
gradually  become  rounded  as  at  p,  or  if  the  crater  ring  is  still  left,  as  at  /.  The 
flattened  floors  of  the  larger  craters  on  the  Moon  are  illustrated  by  #,  while  the 
terrace  and  central  peak  are  shown  at  k. 

With  the  exception  of  the  crater  pits,  nearly  all  the  smaller  depressions  upon  the 
Moon  are  crater  bowls,  and  they  outnumber  at  least  ten  times  all  the  other  depres- 
sions put  together.  The  smallest  crater  rings  are  about  five  miles  in  diameter. 
One  of  the  largest  and  best  situated  crater  bowls  is  Triesnecker,  14  miles  in  diameter. 
It  has  an  inconspicuous  central  peak.  In  the  smaller  bowls  this  feature  seems  to  be 
lacking.  A  well-graduated  series  of  bowls  is  shown  in  the  interior  of  Clavius, 
Figure  16.  The  process  which  converts  a  pit  I  into  a  bowl  p  upon  the  Earth  is  due 
chiefly  to  the  action  of  water.  Upon  the  Moon,  even  in  former  times,  water  was 
probably  scarce,  but  owing  to  the  extremely  rarefied  atmosphere  the  extremes  of 
temperature  are  excessive.  A  range  of  300°  C.  or  540°  F.  occurs  every  fortnight, 
and  it  seems  likely  that  a  considerable  destruction  of  ridges  and  filling  of  hollows 
would  be  due  to  this  cause  by  itself. 

Another  explanation  of  crater  bowls  is  given  by  Gilbert  in  his  dissertation  on 
"  The  Moon's  Face,"  Philosophical  Society  of  Washington,  Bulletin  XII,  251,  where 
he  suggests  that  they  may  be  due  to  a  single  explosion  of  steam,  like  the  terrestrial 
"  maars."  This  seems  improbable,  since  volcanic  features  due  to  steam  are  notably 
absent  from  the  Moon.  On  Hualalai  the  crater  bowls  have  smooth  lava  walls  which 
are  not  at  all  fragmentary,  as  would  be  the  case  were  they  due  to  an  explosion. 


1'ICKERING.  —  LUNAR  AND   HAWAIIAN   PHYSICAL   FEATURES   COMPARED.  169 

In  drawing  the  sections  on  p.  171,  it  was  necessary  to  represent  them  on  several 
different  scales.  The  smallest  scale  adopted  was  T¥JTT  or  a  quarter  of  an  inch  to 
1000  feet.  The  dimensions  of  all  save  a,  b,  and  d  are  based  only  on  estimates,  but 
these  were  made  on  the  spot  with  all  possible  care,  excepting  c  and  e,  where  the 
estimates  were  based  on  photographs,  and  o,  for  which  I  had  to  depend  on  my 
memory.  All  the  sketches  were  either  made  on  the  spot  or  were  taken  from 
photographs.  The  craters  on  Hualalai  are  designated  for  lack  of  a  better  system  of 
nomenclature  in  the  order  in  which  we  visited  them  from  Huehue.  Number  8  is 
the  summit  crater.  In  the  description  which  follows,  the  length  of  1000  feet  is 
given  in  each  case  in  inches  as  measured  on  the  section. 

a  Tuff  cone.     Punch  Bowl,  £  inch. 
b  Tuff  cone.    Diamond  Head,  \  inch, 
c   Cinder  cone  on  Mauna  Kea,  1  inch. 
d  Lava  pit.     Kilauea,  \  inch. 
e    Lava  cone  in  Haleakala,  1  inch. 

/  Lava  pit     Kauohi  or  Sixth  Crater  near  Kilauea,  \  inch. 
g  Lava  cone  and  ring.     Crater  number  10  on  Hualalai,  2  inches. 
h   Lava  ring.     On  floor  of  crater  number  10  on  Hualalai,  8  inches. 
i    Lava  ring  on  Mauna  Loa,  2  inches. 
j   Lava  bowl.     Crater  number  9  on  Hualalai,  1  inch. 
k  Lava  pit.     Crater  number  11  on  Hualalai,  2  inches. 
I    Lava  pit.    Crater  number  3  on  Hualalai,  2  inches. 
m  Lava  pit.     Crater  number  6  on  Hualalai,  2  inches. 
n  Lava  pit.     Crater  number  12  on  Hualalai,  1  inch. 
o  Lava  pit.     Alealea  or  Fourth  Crater  near  Kilauea,  £  inch. 
p  Lava  pit     Crater  number  7  on  Hualalai,  4  inches. 

After  the  craters,  among  the  most  important  features  of  the  lava  flows  are  the 
elevated  formations,  —  the  spiracles,  pinnacles,  and  ridges.  When  the  gases  work 
their  way  up  to  the  surface  from  a  subterranean  cavity  they  escape  by  little 
apertures  called  blow  holes.  In  so  doing  they  often  carry  small  quantities  of 
lava  along  with  them.  This  lava  quickly  hardens  on  reaching  the  surface  and 
builds  up  a  tube  around  the  aperture  which  we  have  called  a  spiracle.  Some- 
times it  is  closed  at  the  top  by  the  last  escaping  lava,  and  sometimes  it  is  left 
open.  These  spiracles  are  found  of  all  sizes,  from  one  measuring  three  or  four 
inches  in  diameter,  up  to  another  measuring  one  hundred  feet.  The  former,  found 
in  Kilauea,  was  twelve  inches  in  height,  and  contained  a  hole  one  inch  in  diameter 
running  its  whole  length,  except  where  it  was  closed  at  the  top.  The  latter  was  found 
on  Hualalai,  and  will  be  described  presently. 


170  PICKERING. LUNAR    AND    HAWAIIAN    PHYSICAL    FEATURES    COMPARED. 

Figure  23  represents  a  spiracle  fourteen  feet  in  height  by  six  feet  in  diameter  at 
its  base,  found  in  Kilauea  near  Halernaumau.  It  is  built  up  of  what  may  be  described 
as  great  drops  of  solidified  lava.  The  interior  tube  is  open  at  the  top  and  measures 
a  foot  in  diameter.  Another  somewhat  smaller  spiracle  is  seen  in  the  background. 
Often  several  spiracles  occur  side  by  side  with  confluent  bases,  as  in  Figure  24.  This 
object  is  also  located  in  Kilauea,  near  the  corral  where  the  horses  are  left.  It  closely 
resembles  the  central  j>eak  or  range  of  peaks  so  often  found  in  the  lunar  craters,  and 
is  doubtless  due  to  the  same  cause.  See  Tycho  and  Longomontanus,  Figure  16.  It 
is  ten  feet  in  height.  Several  of  the  spiracles  forming  it  are  open,  and  several  are 
closed.  There  are  a  number  of  large  cavities  in  the  interior,  in  some  of  which  were 
found  some  very  slender  lava  stalactites.  No  lava  flow  had  escaped  from  any  of  the 
craters,  but  two  outbursts  had  occurred  upon  the  side,  and  may  be  seen  about  half 
way  down  the  slope,  below  the  right-hand  summit  of  the  ridge. 

Figure  25  shows  a  much  larger  row  of  spiracles  found  on  Hualalai.  They  measure 
about  a  thousand  feet  in  height  above  their  base.  Midway  between  the  two  highest 
summits  are  two  smaller  ones.  The  left  hand  of  these  is  known  as  the  Bottomless 
Pit.  The  little  cone  measures  one  hundred  feet  in  diameter  at  its  base  by  sixty  feet 
in  height.  A  narrow  tube  a  few  yards  in  diameter  opens  at  the  summit,  and  it  is 
said  that  it  has  been  sounded  for  1400  feet  without  reaching  bottom.  Whether 
this  figure  is  correct  or  not,  doubtless  the  tube  is  very  deep,  and  no  bottom  is 
visible.  These  spiracles  equal  in  height  many  of  the  central  peaks  found  upon  the 
Moon. 

Sometimes  a  row  of  small  conical  elevations,  about  equally  spaced,  occurs  upon 
the  Moon.  Such  a  row  is  found  in  the  eastern  part  of  the  floor  of  Wilhelm  I,  the  large 
crater  shown  in  the  lower  right-hand  corner  of  Figure  16.  The  illustration  is  on  too 
small  a  scale  to  show  them  to  advantage,  however.  A  row  of  still  larger  cones  is  found 
just  outside  and  northeast  of  the  crater.  They  seem  like  spiracles  thrown  up  along 
the  course  of  a  steam  crack. 

Sometimes  the  lava  slabs  pile  up  on  one  another  in  horizontal  layers,  as  in 
Figure  26,  and  sometimes  much  more  irregular  blocks  occur,  without  any  apparent 
order.  These  form  pinnacles  with  very  steep  sides  and  ends.  Their  origin  seems  to 
be  due  to  recent  flows  of  lava  which  have  transported  and  piled  up  the  fragments 
formed  from  the  earlier  flows,  somewhat  as  the  ice  pack  is  transported  by  the  winds 
and  currents  in  the  far  north.  This  object  was  found  in  Kilauea. 

Another  type  of  pinnacle  consists  of  a  single  block  of  lava  which  may  rise  as  high 
as  sixty  feet  above  the  surrounding  plain.  The  sides  are  often  precipitous,  and  there 


PICKERING.  —  LUNAR  AND  HAWAIIAN  PHYSICAL  FEATURES   COMPARED.  171 


n 


T 


SECTIONS  OP  CRATERS. 


172  PICKERING.  —  LUNAR  AND    HAWAIIAN   PHYSICAL    FEATURES    COMPARED. 

is  no  summit  crater.  It  is  probably  a  solid  block  fallen  from  a  neighboring  cliff,  that 
had  been  undermined  by  the  liquid  flow,  and  after  floating  awhile  and  being  trans- 
ported, was  now  frozen  in,  in  its  present  position.  Such  a  block  is  shown  in  Figure 
27.  It  is  twenty-five  feet  in  height,  and  was  found  upon  the  floor  of  Haleakala.  A 
second  one  is  shown  in  the  distance.  Similar  objects  are  of  frequent  occurrence  upon 
the  various  maria  of  the  Moon.  Doubtless  they  are  often  formed  as  above  described, 
but  in  many  instances  it  is  evident  that  they  have  been  left  in  their  original  positions, 
while  the  objects  formerly  surrounding  them  have  been  destroyed  by  the  flood  of 
molten  lava.  Innumerable  pinnacles  are  found  upon  the  Mare  Imbrium.  A  num- 
ber of  them  are  shown  in  Figure  28.  The  large  crater  in  the  photograph,  near  the 
left-hand  edge,  is  Euler.  Its  diameter  is  nineteen  miles. 

A  curious  feature  in  Hawaii  is  the  very  extensive  series  of  caves  that  penetrate 
the  lava,  especially  the  flows  from  Manna  Loa.  Indeed,  so  many  of  them  have  been 
found  that  it  has  been  suggested  that  they  make  up  an  appreciable  part  of  the  bulk 
of  the  mountain.  A  very  accessible  cave  is  situated  a  few  miles  above  the  town  of 
Hilo.  It  is  said  to  extend  two  miles  up  and  two  miles  down  the  mountain  from  the 
entrance,  which  is  a  place  where  the  roof  happened  to  fall  in,  disclosing  the  cavity. 
The  breadth  of  the  cave  is  about  thirty  feet.  Its  height  varies  in  the  portion  that 
we  traversed  from  three  to  ten  feet.  Larger  caves  are  found  in  other  places,  some- 
times, according  to  Button,  being  as  much  as  sixty  or  eighty  feet  in  height,  and  wide 
in  proportion.  Their  origin  is  due  to  the  fact  that  the  surface  of  the  lava  hardens 
first,  and  that  the  lower  portions  meanwhile  flow  away,  leaving  the  cavity.  Small 
caves  occur  on  the  floors  of  Kilauea  and  Haleakala  where,  since  the  floors  are  level, 
the  formation  seems  to  be  duetto  the  collecting  of  gases  under  sufficient  pressure  to 
hold  back  the  lava  until  it  has  had  time  to  solidify.  Sometimes  lava  channels  form 
without  any  roof.  Some  well  marked  channels  and  caves  are  found  two  or  three 
miles  north  of  Huehue  on  the  Kona  coast.  A  lava  channel  was  noted  not  far  from 
the  summit  of  Hualalai,  where  the  path  crosses  an  open  lava  field.  Another  channel 
was  found  in  Kilauea  near  Halemaumau. 

At  first  it  was  thought  that  these  lava  channels  were  analogous  to  the  broad 
grooves  found  upon  the  Moon,  of  which  the  valleys  of  the  Alps  and  of  Rheita  are 
the  most  conspicuous  examples.  The  Valley  of  Rheita  is  shown  in  Figure  31.  It  is 
190  miles  long  by  15  miles  wide.  Several  parallel  valleys  similar  to  these  are  found 
to  the  southwest  of  Pallas,  and  a  less  well  marked  series  to  the  southeast  of  Sinus 
Iridum.  The  great  range  of  the  Altai  Mountains  in  the  southwestern  quadrant  of 
the  Moon  seems  to  form  one  side  of  such  a  valley  constructed  upon  a  very  large 


PICKERING.- LUNAR   AND    HAWAIIAN    PDYSICAL    FEATURES   COMPARED.  173 

scale.     If  so,  the  other  side  must  have  been  destroyed  by  a  subsequent  melting 
leaving  an  unusually  smooth,  light-colored  surface  in  its  place. 

It  was  later  concluded  that  these  valleys  were  produced  by  a  continuous  faulting 
ong  a  line  of  volcanic  weakness,  and  were  therefore  analogous  to  the  craters  where 
instead   the  faulting  extends  in  all  directions  from  a  volcanic  centre.      The  best 
Hawaiian  representative  of  these  grooved  valleys  is  therefore   probably  the  great 
crater  of  Haleakala  (Figure  3),  whose  length  measures  seven  miles  and  its  breadth 
These  are  about  the  relative  proportions  found  in  many  of  the  valleys  south- 
west of  Pallas,  — nor  are  their  dimensions  so  very  diflferent.     The  line  of  six  small 
craters  found  in  the  bottom  of  Haleakala  corresponds  to  the  similar  line  of  small 
craters  found  along  the  minute  rill  in  the  bottom  of  the  Valley  of  the  Alps. 

The  fact  that  often  one  and  sometimes  both  ends  of  the  lunar  valleys  are  closed 
by  high  walls,  as  is  the  case  with  Haleakala,  strengthens  the  second  explanation  of 
their  origin  as  opposed  to  the  earlier  one.  Elongated  craters  forming  an  intermediate 
step  between  the  ordinary  craters  and  the  grooved  valleys  are  of  frequent  occurrence 
upon  the  Moon.  The  largest  of  these  is  Schiller,  in  the  southeastern  quadrant.  A 
nameless  one  is  shown  in  the  lower  left-hand  corner  of  Figure  31,  and  another  in  the 
lower  right-hand  corner  of  Figure  29.  Others  are  shown  on  the  border  of  the  mare 
in  the  same  figure. 

The  lunar  rills  may  be  divided  into  two  classes,  —  rills  and  crater  rills.  The  rills 
proper  are  extremely  numerous  upon  the  Moon.  About  a  thousand  are  already 
known.  The  Ariadaeus  rill,  shown  in  Figure  29,  is  the  widest  and  most  conspicuous 
of  them.  It  measures  three  miles  in  breadth  by  a  little  over  half  a  mile  in  depth,  as 
determined  by  the  shadows  of  the  ridges  that  cross  it  in  various  places.  Like  all  true 
rills  its  course  is  approximately  straight,  or  made  up  of  curves  of  long  radius.  In  its 
bottom  are  several  minute  craterlets  not  shown  in  the  photograph.  Evidently  like 
our  dikes  and  mineral  veins  it  has  been  partially  filled  from  below.  Other  narrower 
rills,  apparently  bottomless,  are  found  on  the  Moon.  Two  much  smaller  parallel  rills 
with  a  north  and  south  direction  are  found  upon  the  mare  to  the  left.  One  of  these 
is  faintly  shown  in  the  photograph.  The  general  view  that  the  rills  are  simply 
cracks  in  the  lunar  surface  is  undoubtedly  correct.  They  occur  most  frequently 
in  formations  of  the  secondary  period,  that  is  in  the  dark  surfaces,  or  if  found  in  the 
primary  formations,  it  is  where  the  surface  has  apparently  been  softened  and  par- 
tially flattened  out  by  the  application  of  heat,  as  in  the  present  instance.  Rills 
are  frequently  found  at  the  edges  of  the  nutria  and  running  parallel  to  them,  as  in 
Serenitatis  and  Humorum. 


174  PICKEKING.  —  LUNAR   AND   HAWAIIAN   PHYSICAL   FEATURES    COMPARED. 

A  large  crack  is  found  in  Kilauea  in  precisely  this  position,  Figure  30.  It  is  from 
6  to  8  feet  wide  and  from  20  to  30  feet  deep  near  the  bridge.  It  is  said  to  be 
about  a  mile  in  length.  A  crack  5  to  20  feet  in  breadth,  and  40  to  200  in  depth, 
by  16  miles  in  length  is  located  southwest  of  the  crater,  and  a  similar  one 
parallel  to  it  is  found  near  by.  Several  cinder  cones  occur  upon  these  cracks  much 
as  crater  pits  do  upon  the  Moon.  The  cracks  themselves  have  been  partly  filled  up, 
but  one  said  to  be  1500  feet  in  depth  and  5  to  15  in  width  is  situated  not  far  from 
the  Sixth  Crater  near  Kilauea. 

Keanakakoi  is  a  small  crater  one  and  a  half  miles  southwest  of  Kilauea  Iki. 
Its  floor  measures  500  feet  in  diameter  and  is  300  feet  below  the  rim.  It  illustrates 
the  craters  having  smooth  floors  upon  the  Moon.  The  lava  surface  itself  is  wonder- 
fully smooth,  but  a  close  inspection  shows  that  it  has  a  convex  surface,  rising  from 
10  to  15  feet  higher  at  the  centre  than  at  the  edges.  In  this  respect  it  also 
resembles  what  we  find  upon  the  Moon.  The  surface  is  slightly  undulating,  the 
hillocks  measuring  perhaps  two  feet  in  height  above  the  depressions,  thus  indicating 
compression  of  the  floor.  The  surface  is  also  everywhere  seamed  with  cracks,  from 
one  to  three  inches  in  breadth,  and  running  in  all  directions.  This  indicates  subse- 
quent contraction.  As  often  occurs  upon  the  Moon,  a  crack  was  found  running 
parallel  to  the  edge  of  the  floor,  and  not  far  from  the  walls.  Seven  prominent  radial 
cracks  were  counted.  The  arrangement  strikingly  resembled  that  of  the  rills  in 
Gassendi.  A  good  map  of  this  crater  is  given  in  "The  Moon,"  by  Neison,  p.  337.  In 
no  place  did  the  cracks  exceed  eight  inches  in  breadth.  Ferns  are  beginning  to 
grow  in  these  here  and  there. 

A  very  different  type  of  crack  is  sometimes  produced  where  the  surface  is  forced 
open  by  a  subterranean  lava  flow,  and  small  craters  and  blow  holes  are  formed 
along  its  length.  Such  a  one  is  found  at  Huehue,  due  to  an  eruption  on  the  slopes 
of  Hualalai  in  1801,  Figure  33.  A  ridge  50  feet  in  height  in  some  places,  and 
carrying  on  its  summit  a  crack  30  feet  wide  by  40  feet  deep,  and  extending  for 
perhaps  a  mile  has  been  produced.  It  is  very  irregular  in  outline. 

Such  a  crack  is  represented  upon  the  Moon  in  Figure  32.  It  is  a  good  illustration 
of  the  crater  rills  so  called,  and  is  known  as  Bullialdus  <£.  The  straight  portion 
measures  40  miles  in  length  by  perhaps  one  and  a  half  in  breadth.  Its  edges  are 
elevated  as  in  its  Hawaiian  representative,  and  are  quite  as  irregular  in  outline  in 
proportion  to  its  size.  The  distinction  between  these  two  types  of  rills  is  not  sharply 
drawn  upon  the  Moon,  and  the  same  rill  sometimes  exhibits  both  types  in  different 
portions  of  its  length,  as  is  the  case  with  three  small  rills  located  on  the  northeastern 


PICKERING.  —  LUNAR  AND   HAWAIIAN   PHYSICAL  FEATURES   COMPARED.  175 

and  southeastern  flanks  of  Copernicus,  within  one  diameter  of  the  crater  rim.  A 
much  larger  and  more  conspicuous  crater  rill  occurs  one  and  a  half  diameters  to  the 
northwest  of  Copernicus.  The  craterlets  in  this  case  are  so  distinct,  however  that 
the  rill-like  character  is  not  so  well  marked. 

Another  type  of  depression  that  is  found  upon  the  Moon  is  known  as  a  river-bed 
from  its  resemblance  to  its  terrestrial  analogue.  Thirty-four  of  them 
have  been  catalogued.  They  have  been  so  fully  described  else- 
where, Annals  of  the  Harvard  College  Observatory,  XXXII,  84,  that 
it  is  unnecessary  to  more  than  refer  to  them  here.  The  figure 
represents  one  of  the  larger  ones.  It  is  found  on  the  slopes  of  Mt 
Hadley.  Its  length  in  a  straight  line  is  50  miles,  and  its  maximum 
breadth  2000  feet.  It  tapers  uniformly  from  one  end  to  the  other. 
In  Figure  6  a  marking  is  found  closely  resembling  one  of  these  river- 
beds. It  is  situated  due  south  of  Kies  and  west  of  Mercator.  Its 
true  character  can  only  be  ascertained  by  visual  observations  made  under  excep- 
tionally favorable  atmospheric  conditions. 

A  favorite  argument  of  those  who  deny  that  water  ever  existed  upon  the 
Moon  is  the  statement  that  if  such  were  the  case,  signs  of  erosion  would  be  found 
upon  its  surface.  In  the  case  of  the  Earth,  where  vast  bodies  of  water  are  present, 
these  signs  are  very  pronounced  in  the  eroded  valleys  of  mountain  regions,  and  the 
alluvial  plains  of  the  more  open  country.  When  we  search  the  coarser  detail  upon 
the  Moon  no  such  signs  are  to  be  found.  This  makes  it  certain  that  large  quantities 
of  water  could  never  have  been  found  upon  its  surface,  nor  indeed  should  we 
expect  such  to  be  the  case  considering  the  small  value  of  the  force  of  gravitation 
existing  there.  If  the  Moon  ever  possessed  any  water  at  all,  it  must  have  been  in 
comparatively  small  quantities,  and  we  should  accordingly  look  among  its  finer  detail 
for  any  evidence  of  its  former  existence. 

Figure    34    represents   Theophilus,  a  crater   some   64   miles  in   diameter.     The 
central  peaks  rise  5000  to  6000  feet  above  the  crater  floor,  and  are  indented  by 
numerous  deep  valleys,  four  being  clearly  shown  in  the  photograph.     It  is  believed 
that  these  valleys  are  due  to  erosion,  and  are  analogous  to  those  shown  in  Figure  I 
This  figure  represents  a  mountain  ridge  just  back  of  Honolulu,  and  was  taken  from 
another  ridge  called  Tantalus.     Similar  valleys  occur  on  the  central  peak  of  Erato 
thenes     In  the  case  of  Copernicus  they  have  cut  so  deeply  that  they  have  acti 
divided  the  central  mass  into  three  distinct  mountains.     The  precipitation  canno 
have    come   from   a   general  atmospheric  circulation,  but  more   likely  from   steam 


176  PICKERING. LUNAR   AND    HAWAIIAN    PHYSICAL    FEATURES    COMPARED. 

expelled  from  the  openings  of  the  spiracles  in  the  central  peaks  themselves.  The 
valleys  seem  to  be  flat  bottomed,  which  would  imply  the  action  of  ice  rather  than 
water.  Indeed,  at  the  present  time  the  central  peaks  of  Theophilus  are  of  a  dazzling 
brilliancy  as  compared  with  their  surroundings.  This,  it  is  believed,  is  due  to  ice. 
The  floors  of  both  Theophilus  and  Copernicus  show  ridges  that  may  be  lateral 
moraines. 

What  we  ordinarily  speak  of  as  the  lunar  day  is  twenty-nine  and  a  half  terrestrial 
days  in  length.  From  the  standpoint  of  climate  it  may  quite  as  properly  be  called 
the  lunar  year.  In  the  latter  case  sunrise  corresponds  to  spring,  and  sunset  to 
autumn.  The  interval  between  them  is  very  nearly  fifteen  of  our  days.  Using  the 
terms  in  this  sense,  we  find  that  there  are  numerous  spots  scattered  over  the  surface 
of  the  Moon  which  as  the  season  progresses  gradually  darken.  They  reach  their 
maximum  development  about  or  soon  after  midsummer,  and  from  thence  on  slowly 
fade  out  and  disappear  with  the  approach  of  autumn.  They  are  widely  distributed 
over  the  surface,  excepting  near  the  poles,  but  develop  most  rapidly  in  the  equatorial 
regions.  It  is  believed  that  these  variable  dark  spots  are  due  to  vegetation. 

One  of  them  is  seen  in  the  northern  part  of  Julius  Caesar,  the  large  crater  just 
north  of  the  Ariadseus  rill,  Figure  29.  Others  are  found  to  the  north  and  east  of  it. 
The  summer  temperature  on  the  Moon  is  about  that  of  our  desert  regions  at  midday. 
The  winter  temperature  approaches  absolute  zero,  but  since  grain  and  other  seeds 
have  been  exposed  without  injury  to  the  temperature  of  liquid  air,  it  seems  clear  that 
even  terrestrial  vegetation  can  stand  a  range  of  temperature  quite  comparable  to  that 
found  upon  the  Moon. 

The  central  area  of  Figure  35  represents  the  crater  Eratosthenes  taken  at  the  time 
of  full  moon.  On  the  photograph  it  measures  an  inch  and  a  quarter  in  diameter,  and 
is  on  a  scale  of  g-^J-^^,  or  thirty-two  miles  to  the  inch.  The  central  peaks  are  pure 
white,  and  cover  an  area  about  one  quarter  of  an  inch  in  diameter.  Northeast  and 
northwest  of  them  are  two  dark  spots  upon  the  floor,  and  southeast  of  the  peaks  is  a 
very  dark  area  lying  partly  on  the  floor  and  partly  on  the  inside  wall.  These  spots 
go  through  various  interesting  changes  in  density  as  the  season  progresses,  at 
times  entirely  disappearing.  In  one  place  a  slow  movement  of  progression  at  the 
rate  of  four  feet  per  hour  has  been  noted.  Outside  of  the  crater,  large  dark  areas 
are  seen,  which  do  not,  however,  lend  themselves  so  readily  to  measurement  as  do 
those  within  it.  Two  dark  lines  lead  away  from  each  of  the  spots  at  the  base  of  the 
central  peaks.  These  lines  are  believed  to  be  analogous  to  the  so-called  canals  of 
Mars. 


PICKERING.  — LUNAR  AND    HAWAIIAN   PHYSICAL   FEATURES    COMPARED.  17? 

Drawings  of  the  Moon  and  planets  show  much  finer  detail  than  it  is  possible  to 

>tam  by  any  photographs.  Figure  37  is  a  drawing  of  Eratosthenes  made  thirty- 
eight  hours  later  in  the  lunation  than  the  photograph.  Few  changes  have  taken 
place  in  the  meantime,  and  the  three  dark  areas  within  the  crater  can  be  readily 
recognized.  It  will  be  noticed  that  numerous  fine  canals  not  at  all  visible  in  the 
photograph  appear  in  the  drawing.  A  much  more  detailed  account  of  this  crater  will 
be  found  in  the  Annals  of  Harvard  College  Observatory,  LIII,  75. 

Since  different  observers  sometimes  represent  the  same  detail  by  different  methods 
of  shading,  and  since  to  some  eyes  fine  markings,  like  canals,  appear  of  much  less 
breadth  than  to  others,  it  is  very  desirable  where  two  drawings  are  to  be  compared, 
that  they  should  both  be,  if  possible,  by  the  same  observer.  The  sketch  of  Mars, 
Figure  38,  was  made  by  the  writer  when  at  the  Lowell  Observatory  in  Arizona.  The 
similarity  in  appearance  of  the  canals  in  these  two  figures,  together  with  their  varia- 
bility under  similar  conditions,  leads  one  to  believe  that  they  are  due  to  the  same 
cause,  namely,  vegetation. 

During  the  summer  of  1904  the  writer  was  able  to  spend  eight  weeks  at  the 
Lowe  Observatory  in  southern  California.  A  considerable  portion  of  his  time  was 
devoted  to  a  study  of  Eratosthenes.  The  interior  was  found  to  be  seamed  by 
numerous  fine  cracks.  Watching  some  of  these  cracks  soon  after  the  sun  rose  upon 
them,  he  was  able  to  see  them  broaden  out  and  change  gradually  into  canals.  It 
is  his  belief  that  the  cracks  gave  out  water  vapor,  which  fertilized  the  vegetation 
along  their  sides  and  in  their  vicinity,  and  that  it  was  the  growth  of  this  vegetation 
that  produced  the  appearance  of  a  canal. 

The  canals  of  Mars  are  on  a  much  larger  scale  than  those  of  the  Moon ;  one  of 
them  indeed  reaches  the  enormous  length  of  3500  miles.  If  they  are  produced 
naturally,  the  surface  of  the  planet  must  be  cracked  in  many  places.  It  is  generally 
thought  that  terrestrial  volcanoes  lie  along  subterranean  cracks  that  do  not  reach  the 
surface.  The  volcanoes  of  the  great  chain  of  the  Andes  lie  along  a  straight  crack 
reaching  from  southern  Peru  to  Terra  del  Fuego,  2500  miles  in  length.  The  vol- 
canoes of  the  Aleutian  Islands  lie  along  a  curved  crack  equally  long.  Since  other 
shorter  lines  of  volcanoes  are  very  numerous  upon  the  Earth,  and  since  countless 
others  existed  in  former  times,  the  cracks  in  the  Earth's  crust  must  be  exceed- 
ingly numerous.  Every  dike  and  mineral  vein  indeed  bears  witness  to  this  fact. 
There  is  no  reason  why  terrestrial  cracks  should  not  be  as  numerous  as  those  upon 
the  Moon.  In  the  case  of  the  Earth  they  have  usually  been  closed,  sometimes  by 
liquid  matter  from  below,  and  sometimes  by  surface  denudation.  There  is  one 


178  PICKERING.  —  LUNAR   AND   HAWAIIAN   PHYSICAL   FEATURES    COMPARED. 

crack,  however,  which  comes  to  the  surface  in  various  places  in  eastern  Asia  and 
western  Africa,  and  stretching  from  the  Dead  Sea  to  Lake  Nyassa,  reaches  the 
enormous  length  of  3500  miles.  The  longest  known  crack  upon  the  Moon,  that 
of  Sirsalis,  measures  about  400  miles. 

It  does  not  necessarily  follow,  however,  even  if  both  the  Martian  and  lunar 
canals  are  due  to  vegetation,  that  the  vegetation  is  watered  in  the  same  manner. 
There  is  certainly  an  atmospheric  circulation  upon  Mars,  giving  rise  to  clouds,  that 
might  aid  materially  any  subterranean  forces.  Annals  of  Harvard  College  Observa- 
tory, LIII,  155.  Whether  these  forces  could  be  directed  intelligently  by  assumed 
intelligent  inhabitants  of  the  planet  we  do  not  know.  The  only  argument  in  favor 
of  the  existence  of  such  inhabitants  is  the  artificial  appearance  of  the  canals.  The 
four  canals  radiating  from  the  little  lake  just  above  the  centre  of  Figure  37  will 
appear  to  some  minds  quite  as  artificial  in  appearance  as  the  four  canals  radiating 
from  the  elongated  lake  to  the  right  of  the  centre  of  Figure  38. 

To  the  southeast  and  southwest  of  Kilauea  lies  a  desert  region  crossed  in  places 
by  steam  cracks.  One  of  the  first  questions  that  I  asked  my  guide  on  reaching  the 
Volcano  House  was  if  any  of  these  cracks  were  still  active.  He  assured  me  that 
such  was  the  case,  and  the  next  day  we  visited  some  that  were  near  Keanakakoi. 
The  desert  was  found  to  be  absolutely  barren  except  for  certain  long,  narrow  strips 
of  vegetation.  These  consisted  chiefly  of  ferns,  some  bushes,  and  a  few  trees.  It 
was  found  that  they  grew  over  the  steam  cracks,  one  of  which  is  shown  in  Figure  39. 
This  particular  crack  was  a  yard  in  width,  over  two  yards  in  depth,  and  about  thirty 
yards  long.  If  the  region  could  have  been  viewed  from  a  slight  elevation  we  should 
have  found  a  system  of  canals  crossing  the  desert,  these  canals  being  due  to  vege- 
tation, and  differing  in  appearance  from  those  found  upon  the  Moon  and  Mars  in  no 
respect  save  size. 


REFERENCE  INDEX  TO   DESCRIPTIONS   OF    THE   ILLUSTRATIONS. 


SECTIONAL  DRAWINGS  ON  PAGE  171. 


Fig.  a.  154,  169,  169. 

"  6.  154,  169,  169. 

«  c.  155,  169,  169. 

"  d.  157,  158,  169,  169. 

«  e.  155,  169,  169. 

"  /.  157,  169. 

"  g.  164,  168,  169. 

"  h.  164,  168,  169. 


Fig.  i.  165,  169. 

"  j.  167,  168,  169. 

"  A;.  157,  165,  167,  168,  169. 

«  I  157,  168,  168,  169. 

«  m.  157,  168,  169. 

"  n.  168,169. 

"  o.  168,  169,  169. 

"  p.  157,  168,  168,  169. 


PHOTOGRAPHS. 


Fig.  1.  154. 

«  2.  155. 

«  3.  155,  158,  165,  173. 

«  4.  156,  158. 

«  5.  156,  157,  167,  168. 

«  6.  156,  164,  175. 

«  7.  157. 

«  8.  157,  166. 

«  9.  158,  164. 

«  10.  158,  158,  164. 

«  11.  159,  159,  160,  165. 

«  12.  160,  163,  167. 

«  13.  160,  163. 

«  14.  157,  160,  161. 

«  15.  157,  164. 

«  16.  161,  164,  167,  168,  170,  170. 

«  17.  166. 

«  18.  165. 

«  19.  166,  166,  168. 

«  20.  166,  166. 


Fig.  21.  166. 

«  22.  167. 

«  23.  170. 

«  24.  170. 

«  25.  170. 

"  26.  170. 

"  27.  172. 

«  28.  172. 

«  29.  157,  173,  173,  176. 

«  30.  174. 

«  31.  157,  172,  173. 

"  32.  161,  174. 

«  33.  174. 

«  34.  175. 

«  35.  157,  176. 

«  36.  175. 

«  37.  177,  178. 

«  38.  177,  178. 

«  39.  178. 


MEMOIRS  AMERICAN  ACADEMY.    VOL.  XIII. 


FIG.    I.     DIAMOND   HEAD 


tf. 


I 


FIG.   2.     CINDER    CONES    ON     MAUNA    KEA 


H.  PICKERING.      LUNAR    AND    HAWAIIAN    PHYSICAL    FEATURES 


OF  THE 

I    UNIVERSITY    ) 

OF 


MEMOIRS  AMERICAN   ACADEMY.    VOL.  XIII. 


FIG.   3.      INTERIOR  OF  HALEAKALA 


FIG.   4.     MAUNA   LOA 


\\ 


.  H.  PICKERING.      LUNAR    AND    HAWAIIAN    PHYSICAL   FEATURES 


MEMOIRS  AMERICAN   ACADEMY.     VOL. 


XIII. 


FIG.   5.     BULLIALDUS 


FIG    6.     KIES  AND  MERCATOR 


FIG.   7.      KAUHAKU       MOLOKAI 


W.  H.  PICKERING.      LUNAR    AND  HAWAIIAN    PHYSICAL    FEATURES 


OF  THE 

UNIVERSITY  ) 

OF 


MEMOIRS  AMERICAN   ACADEMY.    VOL.  XIII. 


FIG.   8.     SIXTH     CRATER    NEAR   KILAUEA 


FIG.  9.      MOKUAWEOWEO.      MAUNA     LOA 


W.  H.  PICKERING.      LUNAR   AND    HAWAIIAN    PHYSICAL    FEATURES 


OF  THE 

UNIVERSITY 

OF 


MEMOIRS   AMERICAN    ACADEMY.   VOL.   XIII. 


FIG.    10.     KILAUEA    FROM     WALDRON  S     LEDGE 


FIG.    I  I.     SLAG    SECTION 


W.  H.  PICKERING.      LUNAR  AND    HAWAIIAN    PHYSICAL    FEATURES 


MEMOIRS   AMERICAN    ACADEMY.   VOL.    XIII. 


& 


FIG.    12.     LAVA    LAKE    IN     KILAUEA 


r 


FIG.    13       LAVA    LAKE     IN     KILAUEA 


\Y 


H.  PICKERING.      LUNAR    AND    HAWAIIAN    PHYSICAL    FEATURES 


OF  THE 

•VERSITY 

OF 

TOR^ 


FIG.    14.     SCHICKARD.     PHOCYLIDES 


FIG.   I  5.     SINUS     IRIOUM 


3fc^    N      V      '    /'         ?'     »' 


FIG.   17.     RIDGES.     MARE     SERENITATIS 


FIGURE  16  is  INVERTED. 


vND  HAWAIIAN    PHYSICAL    FEATURES 


MEMOIRS    AMERICAN    ACADEMY.    VOL.    XIII. 


FIG.    18.     MOKUAWEOWEO.     MAUNA    LOA 


FIG.   19.     CRATERLETS      KILAUEA    IKI 


H.  PICKERING.      LUNAR   AND    HAWAIIAN    PHYSICAL   FEATURES 


OF  THE 

"NIVERSITY 

OF 


MEMOIRS  AMERICAN   ACADEMY.    VOL.  XIII. 


FIG.  20.     TOP    OF    CRATERUET.     KIUAUEA    IKI 


FIG.   21.     CRATER     PIT.     KILAUEA 


w 


.  H.  PICKERING.      LUNAR   AND  HAWAIIAN    PHYSICAL    FEATURES 


V"    OF  THE 

UNIVERSITY 

OF 


MEMOIRS  AMERICAN   ACADEMY.    VOL.  XIII. 


FIG.  22.     PART    OF    CRATER    BOWL.     HUALALAI 


FIG.  23.     SPIRACLES      KILAUEA 


w 


H.  PICKERING.      LUNAR  AND    HAWAIIAN    PHYSICAL    FEATURES 


MEMOIRS  AMERICAN   ACADEMY.    VOL.  XIII. 


FIG     24.     SPIRACLES.     KILAUEA 


FIG.     25.     SPIRACLES.     HUALALAI 


vv 


H.  PICKERING.      LUNAR   AND   HAWAIIAN    PHYSICAL   FEATURES 


OF  THE 

MIVERSITY 


of 


MEMOIRS  AMERICAN   ACADEMY.     VOL.  XIII. 


FIG.  26.     PINNACLE.     KILAUEA 


FIG.  27.     PINNACLE.     HALEAKALA 


W 


H.  PICKERING.      LUNAR   AND   HAWAIIAN    PHYSICAL   FEATURES 


MEMOIRS   AMERICAN    ACADEMY.   VOL.    XIII. 


^T\K^;  ~>r- 
£  -ttvS 


FIG.   28.      PINACLES.      MARE     IMBRIUM 


FIG.   29.     ARIADAEUS    RILL 


FIG.   30.     CRACK.     KILAUEA 


W.  H.  PICKERING.      LUNAR  AND   HAWAIIAN    PHYSICAL   FEATURES 


MEMOIRS   AMERICAN    ACADEMY.    VOL.    XIII. 


FIG.  31.     VALLEY  OF    RHEITA 


FIG.  32.     BULLIALDUS 


FIG.   33.     CRACK.     HUEHUE 


W.  H.  PICKERING.      LUNAR    AND    HAWAIIAN    PHYSICAL    FEATURES 


MEMOIRS   AMERICAN    ACADEMY.    VOL.    XIII. 


FIG.    34.     THEOPHILUS 


FIG.  35.     ERATOSTHENES 


FIG.   36.      EROSION    VALLEYS    FROM    TANTALUS.     OAHU 


W.  H.  PICKERING.      LUNAR    AND    HAWAIIAN    PHYSICAL   FEATURES 


MEMOIRS   AMERICAN    ACADEMY.   VOL.   XII. 


Pt 


FIG.   37.      LUNAR    CANALS 


FIG.  38.     MARTIAN    CANALS 


FIG.   39.     TERRESTRIAL    CANAL    NEAR     KILAUEA 


W.  H.  PICKERING.      LUNAR   AND  HAWAIIAN    PHYSICAL   FEATURES 


WILL.  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


JUN  24  ib45 


LD  21-100m-7,'40  (6936s) 


179098 


